[Security Solution] Add support for GET requests to the Detection Engine health API (#159970)

**Partially addresses:** https://github.com/elastic/kibana/issues/125642

## Summary

The PoC of the Detection Engine health API has been implemented in
https://github.com/elastic/kibana/pull/157155. Now, we need to integrate
it into the
[support-diagnostics](https://github.com/elastic/support-diagnostics)
tool. It looks like the tool requires the APIs it calls to be callable
with the `GET` verb.

This PR makes it possible to call 2 out of 3 health endpoints with
`GET`:

```txt
GET /internal/detection_engine/health/_cluster
```

```txt
GET /internal/detection_engine/health/_space
```

The `GET` routes don't accept any parameters and use the default
parameters instead:

- interval: `last_day`
- granularity: `hour`
- debug: `false`


### Checklist

- [x]
[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)
was added for features that require explanation or tutorials
- [ ] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

### For maintainers

- [x] This was checked for breaking API changes and was [labeled
appropriately](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)

x-pack/plugins/security_solution/common/detection_engine/rule_monitoring/api/detection_engine_health/README.md

@@ -364,6 +364,7 @@ Response:
 
 ```txt
 POST /internal/detection_engine/health/_space
+GET /internal/detection_engine/health/_space
 ```
 
 Get health overview of the current Kibana space. Scope: all detection rules in the space.
@@ -374,12 +375,18 @@ Returns:
 - health stats history within the same interval in the form of a histogram
   (the same stats are calculated over each of the discreet sub-intervals of the whole interval)
 
-Minimal required parameters: empty object.
+Minimal required parameters for the `POST` route: empty object.
 
 ```json
 {}
 ```
 
+The `GET` route don't accept any parameters and use the default parameters instead:
+
+- interval: `last_day`
+- granularity: `hour`
+- debug: `false`
+
 Response:
 
 ```json
@@ -721,14 +728,21 @@ Response:
 
 ```txt
 POST /internal/detection_engine/health/_cluster
+GET /internal/detection_engine/health/_cluster
 ```
 
-Minimal required parameters: empty object.
+Minimal required parameters for the `POST` route: empty object.
 
 ```json
 {}
 ```
 
+The `GET` route don't accept any parameters and use the default parameters instead:
+
+- interval: `last_day`
+- granularity: `hour`
+- debug: `false`
+
 Response:
 
 ```json

x-pack/plugins/security_solution/server/lib/detection_engine/rule_monitoring/api/detection_engine_health/get_cluster_health/get_cluster_health_route.ts

@@ -5,16 +5,21 @@
  * 2.0.
  */
 
+import type { KibanaResponseFactory } from '@kbn/core-http-server';
 import { transformError } from '@kbn/securitysolution-es-utils';
 import { buildRouteValidation } from '../../../../../../utils/build_validation/route_validation';
 import { buildSiemResponse } from '../../../../routes/utils';
 import type { SecuritySolutionPluginRouter } from '../../../../../../types';
 
-import type { GetClusterHealthResponse } from '../../../../../../../common/detection_engine/rule_monitoring';
+import type {
+  GetClusterHealthRequest,
+  GetClusterHealthResponse,
+} from '../../../../../../../common/detection_engine/rule_monitoring';
 import {
   GET_CLUSTER_HEALTH_URL,
   GetClusterHealthRequestBody,
 } from '../../../../../../../common/detection_engine/rule_monitoring';
+import type { IDetectionEngineHealthClient } from '../../../logic/detection_engine_health';
 import { calculateHealthTimings } from '../health_timings';
 import { validateGetClusterHealthRequest } from './get_cluster_health_request';
 
@@ -27,6 +32,27 @@ import { validateGetClusterHealthRequest } from './get_cluster_health_request';
  *   (the same stats are calculated over each of the discreet sub-intervals of the whole interval)
  */
 export const getClusterHealthRoute = (router: SecuritySolutionPluginRouter) => {
+  router.get(
+    {
+      path: GET_CLUSTER_HEALTH_URL,
+      validate: {},
+      options: {
+        tags: ['access:securitySolution'],
+      },
+    },
+    async (context, request, response) => {
+      return handleClusterHealthRequest({
+        response,
+        resolveParameters: () => validateGetClusterHealthRequest({}),
+        resolveDependencies: async () => {
+          const ctx = await context.resolve(['securitySolution']);
+          const healthClient = ctx.securitySolution.getDetectionEngineHealthClient();
+          return { healthClient };
+        },
+      });
+    }
+  );
+
   router.post(
     {
       path: GET_CLUSTER_HEALTH_URL,
@@ -38,36 +64,57 @@ export const getClusterHealthRoute = (router: SecuritySolutionPluginRouter) => {
       },
     },
     async (context, request, response) => {
-      const siemResponse = buildSiemResponse(response);
-
-      try {
-        const params = validateGetClusterHealthRequest(request.body);
-
-        const ctx = await context.resolve(['securitySolution']);
-        const healthClient = ctx.securitySolution.getDetectionEngineHealthClient();
-
-        const clusterHealthParameters = { interval: params.interval };
-        const clusterHealth = await healthClient.calculateClusterHealth(clusterHealthParameters);
-
-        const responseBody: GetClusterHealthResponse = {
-          // TODO: https://github.com/elastic/kibana/issues/125642 Implement the endpoint and remove the `message` property
-          message: 'Not implemented',
-          timings: calculateHealthTimings(params.requestReceivedAt),
-          parameters: clusterHealthParameters,
-          health: {
-            ...clusterHealth,
-            debug: params.debug ? clusterHealth.debug : undefined,
-          },
-        };
-
-        return response.ok({ body: responseBody });
-      } catch (err) {
-        const error = transformError(err);
-        return siemResponse.error({
-          body: error.message,
-          statusCode: error.statusCode,
-        });
-      }
+      return handleClusterHealthRequest({
+        response,
+        resolveParameters: () => validateGetClusterHealthRequest(request.body),
+        resolveDependencies: async () => {
+          const ctx = await context.resolve(['securitySolution']);
+          const healthClient = ctx.securitySolution.getDetectionEngineHealthClient();
+          return { healthClient };
+        },
+      });
     }
   );
 };
+
+interface ClusterHealthRouteDependencies {
+  healthClient: IDetectionEngineHealthClient;
+}
+
+interface HandleClusterHealthRequestArgs {
+  response: KibanaResponseFactory;
+  resolveParameters: () => GetClusterHealthRequest;
+  resolveDependencies: () => Promise<ClusterHealthRouteDependencies>;
+}
+
+const handleClusterHealthRequest = async (args: HandleClusterHealthRequestArgs) => {
+  const { response, resolveParameters, resolveDependencies } = args;
+  const siemResponse = buildSiemResponse(response);
+
+  try {
+    const params = resolveParameters();
+    const { healthClient } = await resolveDependencies();
+
+    const clusterHealthParameters = { interval: params.interval };
+    const clusterHealth = await healthClient.calculateClusterHealth(clusterHealthParameters);
+
+    const responseBody: GetClusterHealthResponse = {
+      // TODO: https://github.com/elastic/kibana/issues/125642 Implement the endpoint and remove the `message` property
+      message: 'Not implemented',
+      timings: calculateHealthTimings(params.requestReceivedAt),
+      parameters: clusterHealthParameters,
+      health: {
+        ...clusterHealth,
+        debug: params.debug ? clusterHealth.debug : undefined,
+      },
+    };
+
+    return response.ok({ body: responseBody });
+  } catch (err) {
+    const error = transformError(err);
+    return siemResponse.error({
+      body: error.message,
+      statusCode: error.statusCode,
+    });
+  }
+};

x-pack/plugins/security_solution/server/lib/detection_engine/rule_monitoring/api/detection_engine_health/get_space_health/get_space_health_route.ts

@@ -5,16 +5,21 @@
  * 2.0.
  */
 
+import type { KibanaResponseFactory } from '@kbn/core-http-server';
 import { transformError } from '@kbn/securitysolution-es-utils';
 import { buildRouteValidation } from '../../../../../../utils/build_validation/route_validation';
 import { buildSiemResponse } from '../../../../routes/utils';
 import type { SecuritySolutionPluginRouter } from '../../../../../../types';
 
-import type { GetSpaceHealthResponse } from '../../../../../../../common/detection_engine/rule_monitoring';
+import type {
+  GetSpaceHealthRequest,
+  GetSpaceHealthResponse,
+} from '../../../../../../../common/detection_engine/rule_monitoring';
 import {
   GET_SPACE_HEALTH_URL,
   GetSpaceHealthRequestBody,
 } from '../../../../../../../common/detection_engine/rule_monitoring';
+import type { IDetectionEngineHealthClient } from '../../../logic/detection_engine_health';
 import { calculateHealthTimings } from '../health_timings';
 import { validateGetSpaceHealthRequest } from './get_space_health_request';
 
@@ -27,6 +32,27 @@ import { validateGetSpaceHealthRequest } from './get_space_health_request';
  *   (the same stats are calculated over each of the discreet sub-intervals of the whole interval)
  */
 export const getSpaceHealthRoute = (router: SecuritySolutionPluginRouter) => {
+  router.get(
+    {
+      path: GET_SPACE_HEALTH_URL,
+      validate: {},
+      options: {
+        tags: ['access:securitySolution'],
+      },
+    },
+    async (context, request, response) => {
+      return handleSpaceHealthRequest({
+        response,
+        resolveParameters: () => validateGetSpaceHealthRequest({}),
+        resolveDependencies: async () => {
+          const ctx = await context.resolve(['securitySolution']);
+          const healthClient = ctx.securitySolution.getDetectionEngineHealthClient();
+          return { healthClient };
+        },
+      });
+    }
+  );
+
   router.post(
     {
       path: GET_SPACE_HEALTH_URL,
@@ -38,34 +64,55 @@ export const getSpaceHealthRoute = (router: SecuritySolutionPluginRouter) => {
       },
     },
     async (context, request, response) => {
-      const siemResponse = buildSiemResponse(response);
-
-      try {
-        const params = validateGetSpaceHealthRequest(request.body);
-
-        const ctx = await context.resolve(['securitySolution']);
-        const healthClient = ctx.securitySolution.getDetectionEngineHealthClient();
-
-        const spaceHealthParameters = { interval: params.interval };
-        const spaceHealth = await healthClient.calculateSpaceHealth(spaceHealthParameters);
-
-        const responseBody: GetSpaceHealthResponse = {
-          timings: calculateHealthTimings(params.requestReceivedAt),
-          parameters: spaceHealthParameters,
-          health: {
-            ...spaceHealth,
-            debug: params.debug ? spaceHealth.debug : undefined,
-          },
-        };
-
-        return response.ok({ body: responseBody });
-      } catch (err) {
-        const error = transformError(err);
-        return siemResponse.error({
-          body: error.message,
-          statusCode: error.statusCode,
-        });
-      }
+      return handleSpaceHealthRequest({
+        response,
+        resolveParameters: () => validateGetSpaceHealthRequest(request.body),
+        resolveDependencies: async () => {
+          const ctx = await context.resolve(['securitySolution']);
+          const healthClient = ctx.securitySolution.getDetectionEngineHealthClient();
+          return { healthClient };
+        },
+      });
     }
   );
 };
+
+interface SpaceHealthRouteDependencies {
+  healthClient: IDetectionEngineHealthClient;
+}
+
+interface HandleSpaceHealthRequestArgs {
+  response: KibanaResponseFactory;
+  resolveParameters: () => GetSpaceHealthRequest;
+  resolveDependencies: () => Promise<SpaceHealthRouteDependencies>;
+}
+
+const handleSpaceHealthRequest = async (args: HandleSpaceHealthRequestArgs) => {
+  const { response, resolveParameters, resolveDependencies } = args;
+  const siemResponse = buildSiemResponse(response);
+
+  try {
+    const params = resolveParameters();
+    const { healthClient } = await resolveDependencies();
+
+    const spaceHealthParameters = { interval: params.interval };
+    const spaceHealth = await healthClient.calculateSpaceHealth(spaceHealthParameters);
+
+    const responseBody: GetSpaceHealthResponse = {
+      timings: calculateHealthTimings(params.requestReceivedAt),
+      parameters: spaceHealthParameters,
+      health: {
+        ...spaceHealth,
+        debug: params.debug ? spaceHealth.debug : undefined,
+      },
+    };
+
+    return response.ok({ body: responseBody });
+  } catch (err) {
+    const error = transformError(err);
+    return siemResponse.error({
+      body: error.message,
+      statusCode: error.statusCode,
+    });
+  }
+};