[Inventory][ECO] Show alerts for entities (#195250)

## Summary

Show alerts related to entities

close #194381 

### Checklist

- change default sorting from last seen to alertsCount
- when alertsCount is not available server side sorting fallbacks to
last seen
- [Change app route from /app/observability/inventory to
/app/inventory](57598d0)
(causing issue when importing observability plugin
- refactoring: move columns into seperate file 




https://github.com/user-attachments/assets/ea3abc5a-0581-41e7-a174-6655a39c1133



### How to test
- run any synthtrace scenario ex`node scripts/synthtrace
infra_hosts_with_apm_hosts.ts`
- create a rule (SLO or apm) 
- click on the alert count

---------

Co-authored-by: kibanamachine <[email protected]>
Co-authored-by: Cauê Marcondes <[email protected]>

x-pack/packages/observability/observability_utils/array/join_by_key.test.ts

@@ -0,0 +1,224 @@
+/*
+ * 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; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import { joinByKey } from './join_by_key';
+
+describe('joinByKey', () => {
+  it('joins by a string key', () => {
+    const joined = joinByKey(
+      [
+        {
+          serviceName: 'opbeans-node',
+          avg: 10,
+        },
+        {
+          serviceName: 'opbeans-node',
+          count: 12,
+        },
+        {
+          serviceName: 'opbeans-java',
+          avg: 11,
+        },
+        {
+          serviceName: 'opbeans-java',
+          p95: 18,
+        },
+      ],
+      'serviceName'
+    );
+
+    expect(joined.length).toBe(2);
+
+    expect(joined).toEqual([
+      {
+        serviceName: 'opbeans-node',
+        avg: 10,
+        count: 12,
+      },
+      {
+        serviceName: 'opbeans-java',
+        avg: 11,
+        p95: 18,
+      },
+    ]);
+  });
+
+  it('joins by a record key', () => {
+    const joined = joinByKey(
+      [
+        {
+          key: {
+            serviceName: 'opbeans-node',
+            transactionName: '/api/opbeans-node',
+          },
+          avg: 10,
+        },
+        {
+          key: {
+            serviceName: 'opbeans-node',
+            transactionName: '/api/opbeans-node',
+          },
+          count: 12,
+        },
+        {
+          key: {
+            serviceName: 'opbeans-java',
+            transactionName: '/api/opbeans-java',
+          },
+          avg: 11,
+        },
+        {
+          key: {
+            serviceName: 'opbeans-java',
+            transactionName: '/api/opbeans-java',
+          },
+          p95: 18,
+        },
+      ],
+      'key'
+    );
+
+    expect(joined.length).toBe(2);
+
+    expect(joined).toEqual([
+      {
+        key: {
+          serviceName: 'opbeans-node',
+          transactionName: '/api/opbeans-node',
+        },
+        avg: 10,
+        count: 12,
+      },
+      {
+        key: {
+          serviceName: 'opbeans-java',
+          transactionName: '/api/opbeans-java',
+        },
+        avg: 11,
+        p95: 18,
+      },
+    ]);
+  });
+
+  it('joins by multiple keys', () => {
+    const data = [
+      {
+        serviceName: 'opbeans-node',
+        environment: 'production',
+        type: 'service',
+      },
+      {
+        serviceName: 'opbeans-node',
+        environment: 'stage',
+        type: 'service',
+      },
+      {
+        serviceName: 'opbeans-node',
+        hostName: 'host-1',
+      },
+      {
+        containerId: 'containerId',
+      },
+    ];
+
+    const alerts = [
+      {
+        serviceName: 'opbeans-node',
+        environment: 'production',
+        type: 'service',
+        alertCount: 10,
+      },
+      {
+        containerId: 'containerId',
+        alertCount: 1,
+      },
+      {
+        hostName: 'host-1',
+        environment: 'production',
+        alertCount: 5,
+      },
+    ];
+
+    const joined = joinByKey(
+      [...data, ...alerts],
+      ['serviceName', 'environment', 'hostName', 'containerId']
+    );
+
+    expect(joined.length).toBe(5);
+
+    expect(joined).toEqual([
+      { environment: 'stage', serviceName: 'opbeans-node', type: 'service' },
+      { hostName: 'host-1', serviceName: 'opbeans-node' },
+      { alertCount: 10, environment: 'production', serviceName: 'opbeans-node', type: 'service' },
+      { alertCount: 1, containerId: 'containerId' },
+      { alertCount: 5, environment: 'production', hostName: 'host-1' },
+    ]);
+  });
+
+  it('uses the custom merge fn to replace items', () => {
+    const joined = joinByKey(
+      [
+        {
+          serviceName: 'opbeans-java',
+          values: ['a'],
+        },
+        {
+          serviceName: 'opbeans-node',
+          values: ['a'],
+        },
+        {
+          serviceName: 'opbeans-node',
+          values: ['b'],
+        },
+        {
+          serviceName: 'opbeans-node',
+          values: ['c'],
+        },
+      ],
+      'serviceName',
+      (a, b) => ({
+        ...a,
+        ...b,
+        values: a.values.concat(b.values),
+      })
+    );
+
+    expect(joined.find((item) => item.serviceName === 'opbeans-node')?.values).toEqual([
+      'a',
+      'b',
+      'c',
+    ]);
+  });
+
+  it('deeply merges objects', () => {
+    const joined = joinByKey(
+      [
+        {
+          serviceName: 'opbeans-node',
+          properties: {
+            foo: '',
+          },
+        },
+        {
+          serviceName: 'opbeans-node',
+          properties: {
+            bar: '',
+          },
+        },
+      ],
+      'serviceName'
+    );
+
+    expect(joined[0]).toEqual({
+      serviceName: 'opbeans-node',
+      properties: {
+        foo: '',
+        bar: '',
+      },
+    });
+  });
+});

x-pack/packages/observability/observability_utils/array/join_by_key.ts

@@ -0,0 +1,60 @@
+/*
+ * 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; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import { UnionToIntersection, ValuesType } from 'utility-types';
+import { merge, castArray } from 'lodash';
+import stableStringify from 'json-stable-stringify';
+
+export type JoinedReturnType<
+  T extends Record<string, any>,
+  U extends UnionToIntersection<T>
+> = Array<
+  Partial<U> & {
+    [k in keyof T]: T[k];
+  }
+>;
+
+type ArrayOrSingle<T> = T | T[];
+
+export function joinByKey<
+  T extends Record<string, any>,
+  U extends UnionToIntersection<T>,
+  V extends ArrayOrSingle<keyof T & keyof U>
+>(items: T[], key: V): JoinedReturnType<T, U>;
+
+export function joinByKey<
+  T extends Record<string, any>,
+  U extends UnionToIntersection<T>,
+  V extends ArrayOrSingle<keyof T & keyof U>,
+  W extends JoinedReturnType<T, U>,
+  X extends (a: T, b: T) => ValuesType<W>
+>(items: T[], key: V, mergeFn: X): W;
+
+export function joinByKey(
+  items: Array<Record<string, any>>,
+  key: string | string[],
+  mergeFn: Function = (a: Record<string, any>, b: Record<string, any>) => merge({}, a, b)
+) {
+  const keys = castArray(key);
+  // Create a map to quickly query the key of group.
+  const map = new Map();
+  items.forEach((current) => {
+    // The key of the map is a stable JSON string of the values from given keys.
+    // We need stable JSON string to support plain object values.
+    const stableKey = stableStringify(keys.map((k) => current[k]));
+
+    if (map.has(stableKey)) {
+      const item = map.get(stableKey);
+      // delete and set the key to put it last
+      map.delete(stableKey);
+      map.set(stableKey, mergeFn(item, current));
+    } else {
+      map.set(stableKey, { ...current });
+    }
+  });
+  return [...map.values()];
+}

x-pack/plugins/observability_solution/inventory/common/entities.ts

@@ -6,6 +6,9 @@
  */
 import { ENTITY_LATEST, entitiesAliasPattern } from '@kbn/entities-schema';
 import {
+  HOST_NAME,
+  SERVICE_ENVIRONMENT,
+  SERVICE_NAME,
   AGENT_NAME,
   CLOUD_PROVIDER,
   CONTAINER_ID,
@@ -15,9 +18,6 @@ import {
   ENTITY_IDENTITY_FIELDS,
   ENTITY_LAST_SEEN,
   ENTITY_TYPE,
-  HOST_NAME,
-  SERVICE_ENVIRONMENT,
-  SERVICE_NAME,
 } from '@kbn/observability-shared-plugin/common';
 import { isRight } from 'fp-ts/lib/Either';
 import * as t from 'io-ts';
@@ -28,8 +28,19 @@ export const entityTypeRt = t.union([
   t.literal('container'),
 ]);
 
+export const entityColumnIdsRt = t.union([
+  t.literal(ENTITY_DISPLAY_NAME),
+  t.literal(ENTITY_LAST_SEEN),
+  t.literal(ENTITY_TYPE),
+  t.literal('alertsCount'),
+]);
+
+export type EntityColumnIds = t.TypeOf<typeof entityColumnIdsRt>;
+
 export type EntityType = t.TypeOf<typeof entityTypeRt>;
 
+export const defaultEntitySortField: EntityColumnIds = 'alertsCount';
+
 export const MAX_NUMBER_OF_ENTITIES = 500;
 
 export const ENTITIES_LATEST_ALIAS = entitiesAliasPattern({
@@ -79,6 +90,7 @@ interface BaseEntity {
   [ENTITY_DISPLAY_NAME]: string;
   [ENTITY_DEFINITION_ID]: string;
   [ENTITY_IDENTITY_FIELDS]: string | string[];
+  alertsCount?: number;
   [key: string]: any;
 }