Add a config option to change whether unread push notification counts are per-message or per-room (#8820)

This PR adds a new config option to the `push` section of the homeserver config, `group_unread_count_by_room`. By default Synapse will group push notifications by room (so if you have 1000 unread messages, if they lie in 55 rooms, you'll see an unread count on your phone of 55).

However, it is also useful to be able to send out the true count of unread messages if desired. If `group_unread_count_by_room` is set to `false`, then with the above example, one would see an unread count of 1000 (email anyone?).

synapse/push/push_tools.py

@@ -12,12 +12,12 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
 from synapse.push.presentable_names import calculate_room_name, name_from_member_event
 from synapse.storage import Storage
+from synapse.storage.databases.main import DataStore
 
 
-async def get_badge_count(store, user_id):
+async def get_badge_count(store: DataStore, user_id: str, group_by_room: bool) -> int:
     invites = await store.get_invited_rooms_for_local_user(user_id)
     joins = await store.get_rooms_for_user(user_id)
 
@@ -34,9 +34,15 @@ async def get_badge_count(store, user_id):
                     room_id, user_id, last_unread_event_id
                 )
             )
-            # return one badge count per conversation, as count per
-            # message is so noisy as to be almost useless
-            badge += 1 if notifs["notify_count"] else 0
+            if notifs["notify_count"] == 0:
+                continue
+
+            if group_by_room:
+                # return one badge count per conversation
+                badge += 1
+            else:
+                # increment the badge count by the number of unread messages in the room
+                badge += notifs["notify_count"]
     return badge