properly persist inbound group session indexes

lib/src/database/database.g.dart

@@ -4978,6 +4978,21 @@ abstract class _$Database extends GeneratedDatabase {
     );
   }
 
+  Future<int> updateInboundGroupSessionIndexes(
+      String indexes, int client_id, String room_id, String session_id) {
+    return customUpdate(
+      'UPDATE inbound_group_sessions SET indexes = :indexes WHERE client_id = :client_id AND room_id = :room_id AND session_id = :session_id',
+      variables: [
+        Variable.withString(indexes),
+        Variable.withInt(client_id),
+        Variable.withString(room_id),
+        Variable.withString(session_id)
+      ],
+      updates: {inboundGroupSessions},
+      updateKind: UpdateKind.update,
+    );
+  }
+
   Future<int> storeUserDeviceKeysInfo(
       int client_id, String user_id, bool outdated) {
     return customInsert(

lib/src/database/database.moor

@@ -164,6 +164,7 @@ dbGetInboundGroupSessionKey: SELECT * FROM inbound_group_sessions WHERE client_i
 dbGetInboundGroupSessionKeys: SELECT * FROM inbound_group_sessions WHERE client_id = :client_id AND room_id = :room_id;
 getAllInboundGroupSessions: SELECT * FROM inbound_group_sessions WHERE client_id = :client_id;
 storeInboundGroupSession: INSERT OR REPLACE INTO inbound_group_sessions (client_id, room_id, session_id, pickle, content, indexes) VALUES (:client_id, :room_id, :session_id, :pickle, :content, :indexes);
+updateInboundGroupSessionIndexes: UPDATE inbound_group_sessions SET indexes = :indexes WHERE client_id = :client_id AND room_id = :room_id AND session_id = :session_id;
 storeUserDeviceKeysInfo: INSERT OR REPLACE INTO user_device_keys (client_id, user_id, outdated) VALUES (:client_id, :user_id, :outdated);
 setVerifiedUserDeviceKey: UPDATE user_device_keys_key SET verified = :verified WHERE client_id = :client_id AND user_id = :user_id AND device_id = :device_id;
 setBlockedUserDeviceKey: UPDATE user_device_keys_key SET blocked = :blocked WHERE client_id = :client_id AND user_id = :user_id AND device_id = :device_id;

lib/src/room.dart

@@ -1872,7 +1872,11 @@ class Room {
       }
       inboundGroupSessions[sessionId].indexes[messageIndexKey] =
           decryptResult.message_index;
-      _storeOutboundGroupSession();
+      // now we persist the udpated indexes into the database.
+      // the entry should always exist. In the case it doesn't, the following
+      // line *could* throw an error. As that is a future, though, and we call
+      // it un-awaited here, nothing happens, which is exactly the result we want
+      client.database?.updateInboundGroupSessionIndexes(json.encode(inboundGroupSessions[sessionId].indexes), client.id, id, sessionId);
       decryptedPayload = json.decode(decryptResult.plaintext);
     } catch (exception) {
       // alright, if this was actually by our own outbound group session, we might as well clear it