Fix authentication interface and service methods for logout and login.

lib/src/services/authentication/authentication_interface.dart

@@ -36,7 +36,11 @@ abstract class ArcaneAuthInterface {
   /// This method terminates the current session and removes any stored tokens.
   /// Returns a `Result` that either contains a `void` on success or an error
   /// message.
-  Future<Result<void, String>> logout();
+  /// Upon a successful logout, the `onLoggedOut` method will be called if it
+  /// has been provided.
+  Future<Result<void, String>> logout({
+    Future<void> Function()? onLoggedOut,
+  });
 
   /// Logs the user in using an optional, generic `T` type of input.
   /// This login method is a generic method that can be used to login with any
@@ -44,6 +48,8 @@ abstract class ArcaneAuthInterface {
   /// and password. Any type of input can be passed in, and it will be handled
   /// by the implementation of the method wihin the specific authentication
   /// service.
+  /// Upon a successful login, the `onLoggedIn` method will be called if it
+  /// has been provided.
   ///
   /// Example:
   /// ```dart

lib/src/services/authentication/authentication_service.dart

@@ -50,13 +50,13 @@ class ArcaneAuthenticationService extends ArcaneService {
   /// Returns a JWT access token if the registered `ArcaneAuthInterface`
   /// provides one. This token is often used in the headers of HTTP requests
   /// to the backend API.
-  Future<String?> get accessToken =>
-      authInterface?.accessToken ?? Future.value("");
+  Future<String?> get accessToken async =>
+      await authInterface?.accessToken ?? Future.value("");
 
   /// Returns a JWT refresh token if the registered `ArcaneAuthInterface`
   /// provides one.
-  Future<String?> get refreshToken =>
-      authInterface?.refreshToken ?? Future.value("");
+  Future<String?> get refreshToken async =>
+      await authInterface?.refreshToken ?? Future.value("");
 
   AuthenticationStatus? _previousModeWhenSettingDebug;
 
@@ -169,11 +169,12 @@ class ArcaneAuthenticationService extends ArcaneService {
 
     if (!isAuthenticated) Result.error("User is not authenticated.");
 
-    final Result<void, String> loggedOut = await authInterface!.logout();
+    final Result<void, String> loggedOut = await authInterface!.logout(
+      onLoggedOut: onLoggedOut,
+    );
 
     if (loggedOut.isSuccess) {
       setUnauthenticated();
-      if (onLoggedOut != null) await onLoggedOut();
     }
 
     _previousModeWhenSettingDebug = null;
@@ -192,11 +193,11 @@ class ArcaneAuthenticationService extends ArcaneService {
 
     final Result<void, String> result = await authInterface!.login(
       input: input,
+      onLoggedIn: onLoggedIn,
     );
 
     if (result.isSuccess) {
       setAuthenticated();
-      if (onLoggedIn != null) await onLoggedIn();
     }
 
     return result;