Notification Handler to handle notifications in foreground (#837)

* changed how the notifications are handled

* local notifications can be decrypted and shown!

* Improved the handling for the mock and for the normal messages

* Avatar images are also displayed

* pr ready, commented some code that is not supposed to be releaaed yet, adjusted some tests and added some source code in the targets

* fixing some swiftlint complaints and removed an unused function

* better swiftlint disable

* addressing PR comments

UnitTests/Sources/NotificationManager/NotificationManagerTests.swift

@@ -22,6 +22,7 @@ import Combine
 final class NotificationManagerTests: XCTestCase {
     var notificationManager: NotificationManager!
     private let clientProxy = MockClientProxy(userID: "@test:user.net")
+    private lazy var mockUserSession = MockUserSession(clientProxy: clientProxy, mediaProvider: MockMediaProvider())
     private let notificationCenter = UserNotificationCenterSpy()
     private var authorizationStatusWasGranted = false
     private var shouldDisplayInAppNotificationReturnValue = false
@@ -35,7 +36,7 @@ final class NotificationManagerTests: XCTestCase {
 
         notificationManager = NotificationManager(notificationCenter: notificationCenter)
         notificationManager.start()
-        notificationManager.setClientProxy(clientProxy)
+        notificationManager.setUserSession(mockUserSession)
     }
     
     func test_whenRegistered_pusherIsCalled() async {