fix: gamepin in uppercase

core/src/main/java/group07/beatbattle/view/JoinCreateView.java

@@ -186,6 +186,17 @@ private Label createGeneratedCodeLabel() {
     private TextField createCodeInputField() {
         gameCodeField = new TextField("", InputFieldStyles.createDefault(game.getMontserratFont()));
         gameCodeField.setMessageText(Strings.enterCode());
+        gameCodeField.setTextFieldFilter((textField, c) -> {
+            char upper = Character.toUpperCase(c);
+            return Character.isLetterOrDigit(upper);
+        });
+        gameCodeField.setTextFieldListener((textField, c) -> {
+            String current = textField.getText();
+            if (current != null && !current.equals(current.toUpperCase())) {
+                textField.setText(current.toUpperCase());
+                textField.setCursorPosition(textField.getText().length());
+            }
+        });
         return gameCodeField;
     }