prevent names longer than 16 chars

src/main/java/fr/insa/clavardator/ui/dialogs/EditUsernameDialogController.java

@@ -45,6 +45,8 @@ public class EditUsernameDialogController implements Initializable {
 	private ButtonPressEvent cancelListener;
 	private UserList userList;
 
+	private final int MAX_LENGTH = 16;
+
 	@FXML
 	private void onConfirm() {
 		setLocked(true);
@@ -101,6 +103,10 @@ public class EditUsernameDialogController implements Initializable {
 	public void onUsernameChange(ObservableValue<? extends String> observable, String oldText, String newText) {
 		setFieldError(State.VALID);
 		confirmButton.setDisable(newText.isEmpty());
+		if (textField.getText().length() > MAX_LENGTH) {
+			String s = textField.getText().substring(0, MAX_LENGTH);
+			textField.setText(s);
+		}
 	}
 
 	public void setMode(Mode mode) {