GODT-2196: Do not generate message updates for unknown labels

During sync a user may continue to perform operations on the server it
is possible we run into a message which has a labelID we are not aware
of. To counter this we issue `CreateMessage` updates with
`IgnoreUnknownMailboxIDs` set to true. Eventually, after sync the state
will resolve itself with events.

internal/user/events.go

@@ -464,7 +464,7 @@ func (user *User) handleCreateMessageEvent(ctx context.Context, event proton.Mes
 				user.log.WithError(err).Error("Failed to remove failed message ID from vault")
 			}
 
-			user.updateCh[full.AddressID].Enqueue(imap.NewMessagesCreated(res.update))
+			user.updateCh[full.AddressID].Enqueue(imap.NewMessagesCreated(false, res.update))
 
 			return nil
 		})

internal/user/sync_flusher.go

@@ -47,7 +47,7 @@ func (f *flusher) push(update *imap.MessageCreated) {
 
 func (f *flusher) flush() {
 	if len(f.updates) > 0 {
-		f.updateCh.Enqueue(imap.NewMessagesCreated(f.updates...))
+		f.updateCh.Enqueue(imap.NewMessagesCreated(true, f.updates...))
 		f.updates = nil
 		f.curChunkSize = 0
 	}