Add background app refresh support (#892)

* Add background app refresh support

* Cleanup: move methods around so delegates are implemented above privates and privates are ordered better

* Add discardableResult on the userSessionStore's refreshRestorationToken

ElementX/Sources/Services/Client/ClientProxyProtocol.swift

@@ -23,6 +23,14 @@ enum ClientProxyCallback {
     case receivedAuthError(isSoftLogout: Bool)
     case receivedNotification(NotificationItemProxyProtocol)
     case updateRestorationToken
+    
+    var isSyncUpdate: Bool {
+        if case .receivedSyncUpdate = self {
+            return true
+        } else {
+            return false
+        }
+    }
 }
 
 enum ClientProxyError: Error {

ElementX/Sources/Services/UserSession/UserSessionStoreProtocol.swift

@@ -41,6 +41,7 @@ protocol UserSessionStoreProtocol {
     func userSession(for client: Client) async -> Result<UserSessionProtocol, UserSessionStoreError>
 
     /// Refresh the restore token of the client for a given session.
+    @discardableResult
     func refreshRestorationToken(for userSession: UserSessionProtocol) -> Result<Void, UserSessionStoreError>
     
     /// Logs out of the specified session.