Admin API for querying rooms where a user is a member (#8306)

Add a new admin API `GET /_synapse/admin/v1/users/<user_id>/joined_rooms` to
list all rooms where a user is a member.

synapse/rest/admin/__init__.py

@@ -49,6 +49,7 @@ from synapse.rest.admin.users import (
     ResetPasswordRestServlet,
     SearchUsersRestServlet,
     UserAdminServlet,
+    UserMembershipRestServlet,
     UserRegisterServlet,
     UserRestServletV2,
     UsersRestServlet,
@@ -209,6 +210,7 @@ def register_servlets(hs, http_server):
     SendServerNoticeServlet(hs).register(http_server)
     VersionServlet(hs).register(http_server)
     UserAdminServlet(hs).register(http_server)
+    UserMembershipRestServlet(hs).register(http_server)
     UserRestServletV2(hs).register(http_server)
     UsersRestServletV2(hs).register(http_server)
     DeviceRestServlet(hs).register(http_server)

synapse/rest/admin/users.py

@@ -683,3 +683,29 @@ class UserAdminServlet(RestServlet):
         await self.store.set_server_admin(target_user, set_admin_to)
 
         return 200, {}
+
+
+class UserMembershipRestServlet(RestServlet):
+    """
+    Get room list of an user.
+    """
+
+    PATTERNS = admin_patterns("/users/(?P<user_id>[^/]+)/joined_rooms$")
+
+    def __init__(self, hs):
+        self.is_mine = hs.is_mine
+        self.auth = hs.get_auth()
+        self.store = hs.get_datastore()
+
+    async def on_GET(self, request, user_id):
+        await assert_requester_is_admin(self.auth, request)
+
+        if not self.is_mine(UserID.from_string(user_id)):
+            raise SynapseError(400, "Can only lookup local users")
+
+        room_ids = await self.store.get_rooms_for_user(user_id)
+        if not room_ids:
+            raise NotFoundError("User not found")
+
+        ret = {"joined_rooms": list(room_ids), "total": len(room_ids)}
+        return 200, ret