Make description text configurable

Currently, description is hard coded as "Widget" in /src/Plugin/Field/FieldFormatter/StripeCheckoutFormatter on line 86.

          // @todo Make configurable.
          'description' => 'Widget',

To make this configurable, we need a second second setting form field.

For this, I recommend changing the function:

  public static function defaultSettings() {
    return [
      'link_text' => 'Purchase - [price]',
    ] + parent::defaultSettings();
  }

  /**
   * {@inheritdoc}
   */
  public function settingsForm(array $form, FormStateInterface $form_state) {
    return [
        'link_text' => [
          '#type' => 'textfield',
          '#description' => 'The text that will be displayed for the purchase button.',
          '#default value' => $this->getSetting('link_text'),
          '#required' => TRUE,
        ]
    ] + parent::settingsForm($form, $form_state);
  }

  /**
   * {@inheritdoc}
   */
  public function settingsSummary() {
    $summary = [];
    $summary[] = $this->getSetting('link_text');

    return $summary;
  }

to:

  public static function defaultSettings() {
    return [
      'link_text' => 'Purchase - [price]',
      'description_text' => 'Widget',
    ] + parent::defaultSettings();
  }

  /**
   * {@inheritdoc}
   */
  public function settingsForm(array $form, FormStateInterface $form_state) {
    $form = parent::settingsForm($form, $form_state);
    
    $form['link_text'] = [
          '#type' => 'textfield',
          '#description' => 'The text that will be displayed for the purchase button.',
          '#default value' => $this->getSetting('link_text'),
          '#required' => TRUE,
        ]
    ];
    $form['description_text'] = [
          '#type' => 'textfield',
          '#description' => 'The text that will be displayed in the Stripe Checkout widget.',
          '#default value' => $this->getSetting('description_text'),
          '#required' => TRUE,
        ]
    ];        
  }

  /**
   * {@inheritdoc}
   */
  public function settingsSummary() {
    $summary = [];
    $summary[] = $this->getSetting('link_text');
    $summary[] = $this->getSetting('description_text');

    return $summary;
  }

Then:

          'description' => $this->getSetting('description_text'),

Patch forthcoming.