Issue #2862752 by Jo Fitzgerald, phenaproxima: Add documentation to PerComponentEntityFormDisplay destination plugin

core/modules/migrate/src/Plugin/migrate/destination/PerComponentEntityFormDisplay.php

@@ -5,6 +5,38 @@ namespace Drupal\migrate\Plugin\migrate\destination;
 /**
  * This class imports one component of an entity form display.
  *
+ * Destination properties expected in the imported row:
+ * - entity_type: The entity type ID.
+ * - bundle: The entity bundle.
+ * - form_mode: The machine name of the form mode.
+ * - field_name: The machine name of the field to be imported into the display.
+ * - options: (optional) An array of options for displaying the field in this
+ *   form mode.
+ *
+ * Examples:
+ *
+ * @code
+ * source:
+ *   constants:
+ *     entity_type: node
+ *     field_name: comment
+ *     form_mode: default
+ *     options:
+ *       type: comment_default
+ *       weight: 20
+ * process:
+ *   entity_type: 'constants/entity_type'
+ *   field_name: 'constants/field_name'
+ *   form_mode: 'constants/form_mode'
+ *   options: 'constants/options'
+ *   bundle: node_type
+ * destination:
+ *   plugin: component_entity_form_display
+ * @endcode
+ *
+ * This will add a "comment" field on the "default" form mode of the "node"
+ * entity type with options defined by the "options" constant.
+ *
  * @MigrateDestination(
  *   id = "component_entity_form_display"
  * )