#53 - Refactored various components:

- updated the authentication coordinator to use async await
- replaced the UserSession with a ClientProxy (similar to the RoomProxy)
- renamed `completion` to `callback` on the coordinators and view models
- renamed `viewModelResult` to `viewModelAction`
- introduced back UserSession as a user specific service container

ElementX/Sources/Services/Session/UserSession.swift

@@ -0,0 +1,19 @@
+//
+//  UserSession.swift
+//  ElementX
+//
+//  Created by Stefan Ceriu on 27/05/2022.
+//  Copyright © 2022 element.io. All rights reserved.
+//
+
+import Foundation
+
+class UserSession: UserSessionProtocol {
+    let clientProxy: ClientProxyProtocol
+    let mediaProvider: MediaProviderProtocol
+    
+    init(clientProxy: ClientProxyProtocol, mediaProvider: MediaProviderProtocol) {
+        self.clientProxy = clientProxy
+        self.mediaProvider = mediaProvider
+    }
+}