Cleanup the background task that pauses the SDK when resigning active (#903)

* checking if the stop taskHandle is finished before stopping the bg task

* stopping the sync in background now works properly

* this will prevent the case in which if the app suspends and then is immediately foregrounded again, we do not start the sync

* now works as intended

* code improvement

* improved the code a bit

ElementX/Sources/Services/Client/ClientProxyProtocol.swift

@@ -81,9 +81,15 @@ protocol ClientProxyProtocol: AnyObject, MediaLoaderProtocol {
     var allRoomsSummaryProvider: RoomSummaryProviderProtocol? { get }
     
     var invitesSummaryProvider: RoomSummaryProviderProtocol? { get }
+
+    var isSyncing: Bool { get }
     
     func startSync()
-    
+
+    /// Stops the sync usiung non escaping closure.
+    /// It's supposed to be used for the expiration handlers to guarantee its synchronous execution
+    func stopSync(completionHandler: () -> Void)
+
     func stopSync()
     
     func directRoomForUserID(_ userID: String) async -> Result<String?, ClientProxyError>