[Logstash Plugin] Migrate authc.getCurrentUser usage to coreContext.security (#187180)

Part of https://github.com/elastic/kibana/issues/186574

## Summary

This PR migrates the Logstash Plugin's route handler for saving a
pipeline, which consumes `authc.getCurrentUser`, to use
`coreContext.security`.

Background: This PR serves as an example of a plugin migrating away from
depending on the Security plugin, which is a high priority effort for
the last release before 9.0.

### Checklist

Delete any items that are not applicable to this PR.

- [ ] [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

---------

Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>

x-pack/plugins/logstash/server/plugin.ts

@@ -8,12 +8,10 @@
 import { CoreSetup, CoreStart, Logger, Plugin, PluginInitializerContext } from '@kbn/core/server';
 import { LicensingPluginSetup } from '@kbn/licensing-plugin/server';
 import { PluginSetupContract as FeaturesPluginSetup } from '@kbn/features-plugin/server';
-import { SecurityPluginSetup } from '@kbn/security-plugin/server';
 import { registerRoutes } from './routes';
 
 interface SetupDeps {
   licensing: LicensingPluginSetup;
-  security?: SecurityPluginSetup;
   features: FeaturesPluginSetup;
 }
 
@@ -27,7 +25,7 @@ export class LogstashPlugin implements Plugin {
   setup(core: CoreSetup, deps: SetupDeps) {
     this.logger.debug('Setting up Logstash plugin');
 
-    registerRoutes(core.http.createRouter(), deps.security);
+    registerRoutes(core.http.createRouter());
 
     deps.features.registerElasticsearchFeature({
       id: 'pipelines',

x-pack/plugins/logstash/server/routes/index.ts

@@ -5,7 +5,6 @@
  * 2.0.
  */
 
-import { SecurityPluginSetup } from '@kbn/security-plugin/server';
 import type { LogstashPluginRouter } from '../types';
 import { registerClusterLoadRoute } from './cluster';
 import {
@@ -15,12 +14,12 @@ import {
 } from './pipeline';
 import { registerPipelinesListRoute, registerPipelinesDeleteRoute } from './pipelines';
 
-export function registerRoutes(router: LogstashPluginRouter, security?: SecurityPluginSetup) {
+export function registerRoutes(router: LogstashPluginRouter) {
   registerClusterLoadRoute(router);
 
   registerPipelineDeleteRoute(router);
   registerPipelineLoadRoute(router);
-  registerPipelineSaveRoute(router, security);
+  registerPipelineSaveRoute(router);
 
   registerPipelinesListRoute(router);
   registerPipelinesDeleteRoute(router);

x-pack/plugins/logstash/server/routes/pipeline/save.ts

@@ -9,15 +9,11 @@ import { schema } from '@kbn/config-schema';
 import { i18n } from '@kbn/i18n';
 
 import { wrapRouteWithLicenseCheck } from '@kbn/licensing-plugin/server';
-import { SecurityPluginSetup } from '@kbn/security-plugin/server';
 import { Pipeline } from '../../models/pipeline';
 import { checkLicense } from '../../lib/check_license';
 import type { LogstashPluginRouter } from '../../types';
 
-export function registerPipelineSaveRoute(
-  router: LogstashPluginRouter,
-  security?: SecurityPluginSetup
-) {
+export function registerPipelineSaveRoute(router: LogstashPluginRouter) {
   router.put(
     {
       path: '/api/logstash/pipeline/{id}',
@@ -39,14 +35,12 @@ export function registerPipelineSaveRoute(
     wrapRouteWithLicenseCheck(
       checkLicense,
       router.handleLegacyErrors(async (context, request, response) => {
+        const coreContext = await context.core;
         try {
-          let username: string | undefined;
-          if (security) {
-            const user = await security.authc.getCurrentUser(request);
-            username = user?.username;
-          }
+          const user = coreContext.security.authc.getCurrentUser();
+          const username = user?.username;
 
-          const { client } = (await context.core).elasticsearch;
+          const { client } = coreContext.elasticsearch;
           const pipeline = Pipeline.fromDownstreamJSON(request.body, request.params.id, username);
 
           await client.asCurrentUser.logstash.putPipeline({

x-pack/plugins/logstash/tsconfig.json

@@ -16,7 +16,6 @@
 
     "@kbn/features-plugin",
     "@kbn/licensing-plugin",
-    "@kbn/security-plugin",
     "@kbn/i18n",
     "@kbn/i18n-react",
     "@kbn/test-jest-helpers",