[APM] Agent remote configuration (#39555)

* [APM] Agent remote configuration UI
  - Creates apmCm index mapping on plugin initialization.
  - Links from home page to settings page

src/legacy/core_plugins/apm_oss/index.js

@@ -38,6 +38,7 @@ export default function apmOss(kibana) {
         spanIndices: Joi.string().default('apm-*'),
         metricsIndices: Joi.string().default('apm-*'),
         onboardingIndices: Joi.string().default('apm-*'),
+        cmIndex: Joi.string().default('.apm-cm')
       }).default();
     },
 
@@ -48,7 +49,8 @@ export default function apmOss(kibana) {
         'transactionIndices',
         'spanIndices',
         'metricsIndices',
-        'onboardingIndices'
+        'onboardingIndices',
+        'cmIndex'
       ].map(type => server.config().get(`apm_oss.${type}`))));
     }
   });

x-pack/legacy/plugins/apm/public/components/app/Main/Home.tsx

@@ -4,14 +4,20 @@
  * you may not use this file except in compliance with the Elastic License.
  */
 
-import { EuiFlexGroup, EuiFlexItem, EuiTitle } from '@elastic/eui';
+import {
+  EuiFlexGroup,
+  EuiFlexItem,
+  EuiTitle,
+  EuiButtonEmpty
+} from '@elastic/eui';
 import { i18n } from '@kbn/i18n';
 import React from 'react';
 import { ApmHeader } from '../../shared/ApmHeader';
 import { HistoryTabs, IHistoryTab } from '../../shared/HistoryTabs';
 import { SetupInstructionsLink } from '../../shared/Links/SetupInstructionsLink';
 import { ServiceOverview } from '../ServiceOverview';
 import { TraceOverview } from '../TraceOverview';
+import { APMLink } from '../../shared/Links/APMLink';
 
 const homeTabs: IHistoryTab[] = [
   {
@@ -32,6 +38,10 @@ const homeTabs: IHistoryTab[] = [
   }
 ];
 
+const SETTINGS_LINK_LABEL = i18n.translate('xpack.apm.settingsLinkLabel', {
+  defaultMessage: 'Settings'
+});
+
 export function Home() {
   return (
     <div>
@@ -42,6 +52,13 @@ export function Home() {
               <h1>APM</h1>
             </EuiTitle>
           </EuiFlexItem>
+          <EuiFlexItem grow={false}>
+            <APMLink path="/settings">
+              <EuiButtonEmpty size="s" color="primary" iconType="gear">
+                {SETTINGS_LINK_LABEL}
+              </EuiButtonEmpty>
+            </APMLink>
+          </EuiFlexItem>
           <EuiFlexItem grow={false}>
             <SetupInstructionsLink />
           </EuiFlexItem>

x-pack/legacy/plugins/apm/public/components/app/Main/route_config/index.tsx

@@ -14,6 +14,7 @@ import { TransactionDetails } from '../../TransactionDetails';
 import { Home } from '../Home';
 import { BreadcrumbRoute } from '../ProvideBreadcrumbs';
 import { RouteName } from './route_names';
+import { SettingsList } from '../../Settings/SettingsList';
 
 interface RouteParams {
   serviceName: string;
@@ -47,6 +48,15 @@ export const routes: BreadcrumbRoute[] = [
     }),
     name: RouteName.SERVICES
   },
+  {
+    exact: true,
+    path: '/settings',
+    component: SettingsList,
+    breadcrumb: i18n.translate('xpack.apm.breadcrumb.listSettingsTitle', {
+      defaultMessage: 'Settings'
+    }),
+    name: RouteName.SETTINGS
+  },
   {
     exact: true,
     path: '/traces',

x-pack/legacy/plugins/apm/public/components/app/Main/route_config/route_names.tsx

@@ -14,5 +14,6 @@ export enum RouteName {
   ERROR = 'error',
   METRICS = 'metrics',
   TRANSACTION_TYPE = 'transaction_type',
-  TRANSACTION_NAME = 'transaction_name'
+  TRANSACTION_NAME = 'transaction_name',
+  SETTINGS = 'settings'
 }