[Discover][Saved Query] Add schema for Saved Query SO (#154230)

## Summary

A follow up for https://github.com/elastic/kibana/pull/153131
This PR adds schema for Saved Query SO type.

src/core/server/integration_tests/saved_objects/migrations/group2/check_registered_types.test.ts

@@ -123,7 +123,7 @@ describe('checking migration metadata changes on all registered SO types', () =>
         "osquery-pack": "edd84b2c59ef36214ece0676706da8f22175c660",
         "osquery-pack-asset": "18e08979d46ee7e5538f54c080aec4d8c58516ca",
         "osquery-saved-query": "f5e4e303f65c7607248ea8b2672f1ee30e4fb15e",
-        "query": "ec6000b775f06f81470df42d23f7a88cb31d64ba",
+        "query": "cfc049e1f0574fb4fdb2d653d7c10bdc970a2610",
         "rules-settings": "9854495c3b54b16a6625fb250c35e5504da72266",
         "sample-data-telemetry": "c38daf1a49ed24f2a4fb091e6e1e833fccf19935",
         "search": "ed3a9b1681b57d69560909d51933fdf17576ea68",

src/plugins/data/server/saved_objects/query.ts

@@ -8,6 +8,7 @@
 
 import { SavedObjectsType } from '@kbn/core/server';
 import { savedQueryMigrations } from './migrations/query';
+import { SCHEMA_QUERY_V8_8_0 } from './schemas/query';
 
 export const querySavedObjectType: SavedObjectsType = {
   name: 'query',
@@ -29,21 +30,14 @@ export const querySavedObjectType: SavedObjectsType = {
     },
   },
   mappings: {
+    dynamic: false,
     properties: {
       title: { type: 'text' },
       description: { type: 'text' },
-      query: {
-        dynamic: false,
-        properties: {
-          language: { type: 'keyword' },
-        },
-      },
-      filters: {
-        dynamic: false,
-        properties: {},
-      },
-      timefilter: { dynamic: false, properties: {} },
     },
   },
   migrations: savedQueryMigrations,
+  schemas: {
+    '8.8.0': SCHEMA_QUERY_V8_8_0,
+  },
 };

src/plugins/data/server/saved_objects/schemas/query.ts

@@ -0,0 +1,32 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+import { schema } from '@kbn/config-schema';
+
+// As per `SavedQueryAttributes`
+export const SCHEMA_QUERY_V8_8_0 = schema.object({
+  title: schema.string(),
+  description: schema.string({ defaultValue: '' }),
+  query: schema.object({
+    language: schema.string(),
+    query: schema.oneOf([schema.string(), schema.object({}, { unknowns: 'allow' })]),
+  }),
+  filters: schema.maybe(schema.arrayOf(schema.object({}, { unknowns: 'allow' }))),
+  timefilter: schema.maybe(
+    schema.object({
+      from: schema.string(),
+      to: schema.string(),
+      refreshInterval: schema.maybe(
+        schema.object({
+          value: schema.number(),
+          pause: schema.boolean(),
+        })
+      ),
+    })
+  ),
+});