Don't pick a random client to get user profiles

Causes problem if one of the candidate client is on a server that
doesn't federate (e.g. a local one). Move the `get_profile()` function
from Backend to MatrixClient.

src/backend/backend.py

@@ -371,22 +371,6 @@ class Backend:
 
     # Client functions that don't need authentification
 
-    async def get_profile(
-        self, user_id: str, use_cache: bool = True,
-    ) -> nio.ProfileGetResponse:
-        """Cache and return the matrix profile of `user_id`."""
-
-        async with self.get_profile_locks[user_id]:
-            if use_cache and user_id in self.profile_cache:
-                return self.profile_cache[user_id]
-
-            client   = self.clients.get(user_id) or await self.get_any_client()
-            response = await client.get_profile(user_id)
-
-            self.profile_cache[user_id] = response
-            return response
-
-
     async def thumbnail(
         self, server_name: str, media_id: str, width: int, height: int,
     ) -> nio.ThumbnailResponse:

src/backend/matrix_client.py

@@ -431,10 +431,25 @@ class MatrixClient(nio.AsyncClient):
         self.first_sync_done.clear()
 
 
+    async def get_profile(
+        self, user_id: str, use_cache: bool = True,
+    ) -> nio.ProfileGetResponse:
+        """Cache and return the matrix profile of `user_id`."""
+
+        async with self.backend.get_profile_locks[user_id]:
+            if use_cache and user_id in self.backend.profile_cache:
+                return self.backend.profile_cache[user_id]
+
+            response = await super().get_profile(user_id)
+
+            self.backend.profile_cache[user_id] = response
+            return response
+
+
     async def update_own_profile(self) -> None:
         """Fetch our profile from server and Update our model `Account`."""
 
-        resp = await self.backend.get_profile(self.user_id, use_cache=False)
+        resp = await self.get_profile(self.user_id, use_cache=False)
 
         account = self.models["accounts"][self.user_id]
         account.set_fields(
@@ -1928,7 +1943,7 @@ class MatrixClient(nio.AsyncClient):
 
         If the member isn't found in the room (e.g. they left) and
         `can_fetch_from_network` is `True`, their
-        profile is retrieved using `MatrixClient.backend.get_profile()`.
+        profile is retrieved using `MatrixClient.get_profile()`.
         """
 
         try:
@@ -1940,7 +1955,7 @@ class MatrixClient(nio.AsyncClient):
                 return ("", "", True)
 
             try:
-                info = await self.backend.get_profile(user_id)
+                info = await self.get_profile(user_id)
                 return (info.displayname or "", info.avatar_url or "", False)
             except MatrixError:
                 return ("", "", False)