#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/Client/ClientProxyProtocol.swift

@@ -0,0 +1,36 @@
+//
+//  ClientProxyProtocol.swift
+//  ElementX
+//
+//  Created by Stefan Ceriu on 26/05/2022.
+//  Copyright © 2022 element.io. All rights reserved.
+//
+
+import Foundation
+import MatrixRustSDK
+import Combine
+
+enum ClientProxyCallback {
+    case updatedRoomsList
+}
+
+enum ClientProxyError: Error {
+    case failedRetrievingAvatarURL
+    case failedRetrievingDisplayName
+}
+
+protocol ClientProxyProtocol {
+    var callbacks: PassthroughSubject<ClientProxyCallback, Never> { get }
+    
+    var userIdentifier: String { get }
+    
+    var rooms: [RoomProxy] { get }
+    
+    func loadUserDisplayName() async -> Result<String, ClientProxyError>
+        
+    func loadUserAvatarURLString() async -> Result<String, ClientProxyError>
+    
+    func mediaSourceForURLString(_ urlString: String) -> MatrixRustSDK.MediaSource
+    
+    func loadMediaContentForSource(_ source: MatrixRustSDK.MediaSource) throws -> Data
+}