Issue #3254006 by mxh: Make the usage of the label pattern more intuitive

 * @ContentEntityType(

 *   id = "field_bundle",

 *   label = @Translation("Field bundle"),

 *   label_collection = @Translation("Field bundles"),

 *   label_collection = @Translation("Field bundle items"),

 *   bundle_label = @Translation("Field bundle config"),

 *   label_singular = @Translation("field bundle item"),

 *   label_plural = @Translation("field bundle items"),

    }

    $form['label'] = [

      '#title' => $this->t('Label'),

      '#title' => $this->t('Config label'),

      '#type' => 'textfield',

      '#default_value' => $bundle_config->label(),

      '#description' => $this->t('The human-readable config name of this field bundle.'),

      '#description' => $this->t('The human-readable name of this field bundle configuration.'),

      '#required' => TRUE,

      '#size' => 30,

    ];

      '#title' => $this->t('Description'),

      '#type' => 'textarea',

      '#default_value' => $bundle_config->getDescription(),

      '#description' => $this->t('Describe this field bundle. The text will be displayed on the <em>Add new field bundle</em> page.'),

      '#description' => $this->t('Describe this field bundle config. The text will be displayed on the <em>Add field bundle item</em> page.'),

    ];

    $form['label_pattern'] = [

      '#title' => $this->t('Label pattern'),

      '#title' => $this->t('Pattern for automatic label generation'),

      '#type' => 'textfield',

      '#description' => $this->t('Define a pattern to use for creating the label of the field bundle. Tokens are allowed, e.g. [bundle:config-label]. Leave empty to not use any pattern.'),

      '#description' => $this->t('Instead of manually entering a label on each field bundle item within a form, you can define a label pattern here for auto-generating a value for it. This pattern will be applied everytime a field bundle item is being saved. Tokens are allowed, e.g. [bundle:string-representation]. Leave empty to not use a name pattern for items of this bundle config. If a label pattern is being used, you may optionally hide the label field in the <em>Manage form display</em> settings.'),

      '#default_value' => $bundle_config->getLabelPattern(),

      '#size' => 255,

      '#maxlength' => 255,