Send delivery receipt immediately after receiving send response

Previously it would wait for the message ID to come from the echo, but
the echo isn't reliable, so need to do this instead.

Also added a TODO to store the offline threading IDs in the database to
avoid some of the problems that not receiving the message ID can cause.

mautrix_facebook/portal.py

@@ -526,6 +526,9 @@ class Portal(DBPortal, BasePortal):
                                   message: TextMessageEventContent) -> None:
         converted = await matrix_to_facebook(message, self.mxid)
         offline_threading_id = sender.mqtt.generate_offline_threading_id()
+        # TODO store OTI's in the database because sometimes facebook doesn't echo the message back
+        #      immediately. Also need to update things like incoming replies to search the database
+        #      by OTI instead of only message ID. Outgoing replies may be unsolveable.
         self._oti_dedup[offline_threading_id] = event_id
         resp = await sender.mqtt.send_message(self.fbid, self.fb_type != ThreadType.USER,
                                               message=converted.text, mentions=converted.mentions,
@@ -536,6 +539,7 @@ class Portal(DBPortal, BasePortal):
             await self._send_bridge_error(resp.error_message)
         else:
             self.log.debug(f"Handled Matrix message {event_id} -> OTI: {offline_threading_id}")
+            await self._send_delivery_receipt(event_id)
 
     async def _handle_matrix_media(self, event_id: EventID, sender: 'u.User',
                                    message: MediaMessageEventContent) -> None:
@@ -564,7 +568,9 @@ class Portal(DBPortal, BasePortal):
                            f"{resp.debug_info.message}")
             await self._send_bridge_error(f"Media upload error: {resp.debug_info.message}")
             return
+        # TODO put message ID from response to database if oti is still on _oti_dedup
         self.log.debug(f"Handled Matrix message {event_id} -> {resp.message_id} / {oti}")
+        await self._send_delivery_receipt(event_id)
         # send_resp = await sender.mqtt.send_message(self.fbid, self.fb_type != ThreadType.USER,
         #                                            media_ids=[resp.media_id], reply_to=reply_to,
         #                                            offline_threading_id=oti)
@@ -723,7 +729,6 @@ class Portal(DBPortal, BasePortal):
             self._dedup.appendleft(msg_id)
             await DBMessage(mxid=event_id, mx_room=self.mxid, fbid=msg_id, fb_chat=self.fbid,
                             fb_receiver=self.fb_receiver, index=0, timestamp=timestamp).insert()
-            await self._send_delivery_receipt(event_id)
             return
         elif msg_id in self._dedup:
             self.log.trace("Not handling message %s, found ID in dedup queue", msg_id)