Add an admin APIs to allow server admins to list users' pushers (#8610)

Add an admin API `GET /_synapse/admin/v1/users/<user_id>/pushers` like https://matrix.org/docs/spec/client_server/latest#get-matrix-client-r0-pushers

synapse/rest/admin/users.py

@@ -39,6 +39,17 @@ from synapse.types import JsonDict, UserID
 
 logger = logging.getLogger(__name__)
 
+_GET_PUSHERS_ALLOWED_KEYS = {
+    "app_display_name",
+    "app_id",
+    "data",
+    "device_display_name",
+    "kind",
+    "lang",
+    "profile_tag",
+    "pushkey",
+}
+
 
 class UsersRestServlet(RestServlet):
     PATTERNS = historical_admin_path_patterns("/users/(?P<user_id>[^/]*)$")
@@ -713,6 +724,47 @@ class UserMembershipRestServlet(RestServlet):
         return 200, ret
 
 
+class PushersRestServlet(RestServlet):
+    """
+    Gets information about all pushers for a specific `user_id`.
+
+    Example:
+        http://localhost:8008/_synapse/admin/v1/users/
+        @user:server/pushers
+
+    Returns:
+        pushers: Dictionary containing pushers information.
+        total: Number of pushers in dictonary `pushers`.
+    """
+
+    PATTERNS = admin_patterns("/users/(?P<user_id>[^/]*)/pushers$")
+
+    def __init__(self, hs):
+        self.is_mine = hs.is_mine
+        self.store = hs.get_datastore()
+        self.auth = hs.get_auth()
+
+    async def on_GET(
+        self, request: SynapseRequest, user_id: str
+    ) -> Tuple[int, JsonDict]:
+        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")
+
+        if not await self.store.get_user_by_id(user_id):
+            raise NotFoundError("User not found")
+
+        pushers = await self.store.get_pushers_by_user_id(user_id)
+
+        filtered_pushers = [
+            {k: v for k, v in p.items() if k in _GET_PUSHERS_ALLOWED_KEYS}
+            for p in pushers
+        ]
+
+        return 200, {"pushers": filtered_pushers, "total": len(filtered_pushers)}
+
+
 class UserMediaRestServlet(RestServlet):
     """
     Gets information about all uploaded local media for a specific `user_id`.