[Ingest Manager][Endpoint] Add Endpoint Create Policy flow with Ingest (

elastic#68955)

* Ingest: add data-test-subj prop support to Ingest components
* Ingest: Add Context Provider to bridge History from Kibana to Hash router
* Ingest: Added support for route state in Create Datasource page
* Endpoint: Add Create button to Polices List header
* Endpoint: Added support for passing of state from endpoint to ingest on policy
* Endpoint: additional functional test cases

x-pack/plugins/ingest_manager/public/applications/ingest_manager/components/header.tsx

@@ -36,6 +36,7 @@ export interface HeaderProps {
   rightColumn?: JSX.Element;
   rightColumnGrow?: EuiFlexItemProps['grow'];
   tabs?: EuiTabProps[];
+  'data-test-subj'?: string;
 }
 
 const HeaderColumns: React.FC<Omit<HeaderProps, 'tabs'>> = memo(
@@ -53,8 +54,9 @@ export const Header: React.FC<HeaderProps> = ({
   rightColumnGrow,
   tabs,
   maxWidth,
+  'data-test-subj': dataTestSubj,
 }) => (
-  <Container>
+  <Container data-test-subj={dataTestSubj}>
     <Wrapper maxWidth={maxWidth}>
       <HeaderColumns
         leftColumn={leftColumn}

x-pack/plugins/ingest_manager/public/applications/ingest_manager/hooks/use_intra_app_state.tsx

@@ -0,0 +1,65 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+import React, { memo, useContext, useMemo } from 'react';
+import { AppMountParameters } from 'kibana/public';
+import { useLocation } from 'react-router-dom';
+import { AnyIntraAppRouteState } from '../types';
+
+interface IntraAppState<S extends AnyIntraAppRouteState = AnyIntraAppRouteState> {
+  forRoute: string;
+  routeState?: S;
+}
+
+const IntraAppStateContext = React.createContext<IntraAppState>({ forRoute: '' });
+const wasHandled = new WeakSet<IntraAppState>();
+
+/**
+ * Provides a bridget between Kibana's ScopedHistory instance (normally used with BrowserRouter)
+ * and the Hash router used within the app in order to enable state to be used between kibana
+ * apps
+ */
+export const IntraAppStateProvider = memo<{
+  kibanaScopedHistory: AppMountParameters['history'];
+  children: React.ReactNode;
+}>(({ kibanaScopedHistory, children }) => {
+  const internalAppToAppState = useMemo<IntraAppState>(() => {
+    return {
+      forRoute: kibanaScopedHistory.location.hash.substr(1),
+      routeState: kibanaScopedHistory.location.state as AnyIntraAppRouteState,
+    };
+  }, [kibanaScopedHistory.location.hash, kibanaScopedHistory.location.state]);
+  return (
+    <IntraAppStateContext.Provider value={internalAppToAppState}>
+      {children}
+    </IntraAppStateContext.Provider>
+  );
+});
+
+/**
+ * Retrieve UI Route state from the React Router History for the current URL location.
+ * This state can be used by other Kibana Apps to influence certain behaviours in Ingest, for example,
+ * redirecting back to an given Application after a craete action.
+ */
+export function useIntraAppState<S = AnyIntraAppRouteState>():
+  | IntraAppState<S>['routeState']
+  | undefined {
+  const location = useLocation();
+  const intraAppState = useContext(IntraAppStateContext);
+  if (!intraAppState) {
+    throw new Error('Hook called outside of IntraAppStateContext');
+  }
+  return useMemo(() => {
+    // Due to the use of HashRouter in Ingest, we only want state to be returned
+    // once so that it does not impact navigation to the page from within the
+    // ingest app. side affect is that the browser back button would not work
+    // consistently either.
+    if (location.pathname === intraAppState.forRoute && !wasHandled.has(intraAppState)) {
+      wasHandled.add(intraAppState);
+      return intraAppState.routeState as S;
+    }
+  }, [intraAppState, location.pathname]);
+}