Add button to purge rooms to room list

Add button (BulkDeleteButton) to delete rooms with no local users:
- purge rooms `POST /_synapse/admin/v1/purge_room`
(https://github.com/matrix-org/synapse/blob/master/docs/admin_api/purge_room.md)

src/components/rooms.js

@@ -1,12 +1,36 @@
-import React from "react";
-import { Datagrid, List, TextField, Pagination } from "react-admin";
+import React, { Fragment } from "react";
+import {
+  Datagrid,
+  List,
+  TextField,
+  Pagination,
+  BulkDeleteButton,
+  useTranslate,
+} from "react-admin";
 
 const RoomPagination = props => (
   <Pagination {...props} rowsPerPageOptions={[10, 25, 50, 100, 500, 1000]} />
 );
 
+const RoomBulkActionButtons = props => {
+  const translate = useTranslate();
+  return (
+    <Fragment>
+      <BulkDeleteButton
+        {...props}
+        label="resources.rooms.action.purge"
+        title={translate("resources.rooms.helper.purge")}
+      />
+    </Fragment>
+  );
+};
+
 export const RoomList = props => (
-  <List {...props} pagination={<RoomPagination />}>
+  <List
+    {...props}
+    pagination={<RoomPagination />}
+    bulkActionButtons={<RoomBulkActionButtons />}
+  >
     <Datagrid>
       <TextField source="room_id" />
       <TextField source="name" />

src/i18n/de.js

@@ -54,6 +54,13 @@ export default {
         canonical_alias: "Alias",
         joined_members: "Mitglieder",
       },
+      helper: {
+        purge:
+          "Alle lokalen Benutzer müssen den Raum verlassen haben, bevor er entfernt werden kann.",
+      },
+      action: {
+        purge: "Säubere Raum",
+      },
     },
     connections: {
       name: "Verbindungen",

src/i18n/en.js

@@ -54,6 +54,13 @@ export default {
         canonical_alias: "Alias",
         joined_members: "Members",
       },
+      helper: {
+        purge:
+          "All local users must have left the room before it can be removed.",
+      },
+      action: {
+        purge: "Purge room",
+      },
     },
     connections: {
       name: "Connections",

src/synapse/dataProvider.js

@@ -53,6 +53,11 @@ const resourceMap = {
     total: json => {
       return json.total_rooms;
     },
+    delete: id => ({
+      endpoint: "/_synapse/admin/v1/purge_room",
+      body: { room_id: id },
+      method: "POST",
+    }),
   },
   connections: {
     path: "/_synapse/admin/v1/whois",