Rename constant to make it more clear what they are

Author: rolandgeider

lib/helpers/consts.dart

@@ -28,8 +28,8 @@ const DEFAULT_SERVER_PROD = 'https://wger.de';
 const DEFAULT_SERVER_TEST = 'https://wger-master.rge.uber.space/';
 
 // Debug mode Login Data
-const USER_NAME = 'user';
-const PASSWORD = 'flutteruser';
+const TESTSERVER_USER_NAME = 'user';
+const TESTSERVER_PASSWORD = 'flutteruser';
 
 /// Keys used in the android manifest
 const MANIFEST_KEY_API = 'wger.api_key';

lib/screens/auth_screen.dart

@@ -152,8 +152,8 @@ class _AuthCardState extends State<AuthCard> {
   void _preFillTextfields() {
     if (kDebugMode && _authMode == AuthMode.Login) {
       setState(() {
-        _usernameController.text = USER_NAME;
-        _passwordController.text = PASSWORD;
+        _usernameController.text = TESTSERVER_USER_NAME;
+        _passwordController.text = TESTSERVER_PASSWORD;
       });
     }
   }