Add delete room admin endpoint (#7613)

The Delete Room admin API allows server admins to remove rooms from server
and block these rooms.
`DELETE /_synapse/admin/v1/rooms/<room_id>`
It is a combination and improvement of "[Shutdown room](https://github.com/matrix-org/synapse/blob/develop/docs/admin_api/shutdown_room.md)" and "[Purge room](https://github.com/matrix-org/synapse/blob/develop/docs/admin_api/purge_room.md)" API.

Fixes: #6425 

It also fixes a bug in [synapse/storage/data_stores/main/room.py](synapse/storage/data_stores/main/room.py) in ` get_room_with_stats`.
It should return `None` if the room is unknown. But it returns an `IndexError`.
901b1fa561/synapse/storage/data_stores/main/room.py (L99-L105)

Related to:
- #5575
- https://github.com/Awesome-Technologies/synapse-admin/issues/17

Signed-off-by: Dirk Klimpel dirk@klimpel.org

synapse/server.py

@@ -73,7 +73,11 @@ from synapse.handlers.profile import BaseProfileHandler, MasterProfileHandler
 from synapse.handlers.read_marker import ReadMarkerHandler
 from synapse.handlers.receipts import ReceiptsHandler
 from synapse.handlers.register import RegistrationHandler
-from synapse.handlers.room import RoomContextHandler, RoomCreationHandler
+from synapse.handlers.room import (
+    RoomContextHandler,
+    RoomCreationHandler,
+    RoomShutdownHandler,
+)
 from synapse.handlers.room_list import RoomListHandler
 from synapse.handlers.room_member import RoomMemberMasterHandler
 from synapse.handlers.room_member_worker import RoomMemberWorkerHandler
@@ -144,6 +148,7 @@ class HomeServer(object):
         "handlers",
         "auth",
         "room_creation_handler",
+        "room_shutdown_handler",
         "state_handler",
         "state_resolution_handler",
         "presence_handler",
@@ -357,6 +362,9 @@ class HomeServer(object):
     def build_room_creation_handler(self):
         return RoomCreationHandler(self)
 
+    def build_room_shutdown_handler(self):
+        return RoomShutdownHandler(self)
+
     def build_sendmail(self):
         return sendmail