fix: properly fetch participants when transitioning from invite to join

We used to add app the member counts of invited users and joined users,
which would make us assume the participants list is complete. Which
would mean we always return the wrong state.

Additionally there is no need to rely on if we have a cached response.
Instead we always only check for completeness instead of possibly
returning stale responses just because we fetched the members once.

lib/src/room.dart

@@ -1565,8 +1565,6 @@ class Room {
     return <User>[];
   }
 
-  bool _requestedParticipants = false;
-
   /// Request the full list of participants from the server. The local list
   /// from the store is not complete if the client uses lazy loading.
   /// List `membershipFilter` defines with what membership do you want the
@@ -1582,17 +1580,20 @@ class Room {
       ],
       bool suppressWarning = false,
       bool cache = true]) async {
-    if (!participantListComplete && partial) {
+    if (!participantListComplete || partial) {
       // we aren't fully loaded, maybe the users are in the database
+      // We always need to check the database in the partial case, since state
+      // events won't get written to memory in this case and someone new could
+      // have joined, while someone else left, which might lead to the same
+      // count in the completeness check.
       final users = await client.database?.getUsers(this) ?? [];
       for (final user in users) {
         setState(user);
       }
     }
 
-    // Do not request users from the server if we have already done it
-    // in this session or have a complete list locally.
-    if (_requestedParticipants || participantListComplete) {
+    // Do not request users from the server if we have already have a complete list locally.
+    if (participantListComplete) {
       return getParticipants(membershipFilter);
     }
 
@@ -1617,7 +1618,6 @@ class Room {
       }
     }
 
-    _requestedParticipants = cache;
     users.removeWhere((u) => !membershipFilter.contains(u.membership));
     return users;
   }
@@ -1625,10 +1625,14 @@ class Room {
   /// Checks if the local participant list of joined and invited users is complete.
   bool get participantListComplete {
     final knownParticipants = getParticipants();
-    knownParticipants.removeWhere(
-        (u) => ![Membership.join, Membership.invite].contains(u.membership));
-    return knownParticipants.length ==
-        (summary.mJoinedMemberCount ?? 0) + (summary.mInvitedMemberCount ?? 0);
+    final joinedCount =
+        knownParticipants.where((u) => u.membership == Membership.join).length;
+    final invitedCount = knownParticipants
+        .where((u) => u.membership == Membership.invite)
+        .length;
+
+    return (summary.mJoinedMemberCount ?? 0) == joinedCount &&
+        (summary.mInvitedMemberCount ?? 0) == invitedCount;
   }
 
   @Deprecated(