Issue #3083598 by owenbush, the_glitch: Needs plugin to enable configuration with Group module

modules/recurring_events_registration/src/Plugin/GroupContentEnabler/Registrant.php

+<?php
+
+namespace Drupal\recurring_events_registration\Plugin\GroupContentEnabler;
+
+use Drupal\group\Plugin\GroupContentEnablerBase;
+
+/**
+ * Allows Registrant content to be added to groups.
+ *
+ * @GroupContentEnabler(
+ *   id = "registrant",
+ *   label = @Translation("Registrant"),
+ *   description = @Translation("Adds Registrant entities to groups."),
+ *   entity_type_id = "registrant",
+ *   path_key = "registrant",
+ * )
+ */
+class Registrant extends GroupContentEnablerBase {
+}

src/Plugin/GroupContentEnabler/EventInstance.php

+<?php
+
+namespace Drupal\recurring_events\Plugin\GroupContentEnabler;
+
+use Drupal\group\Plugin\GroupContentEnablerBase;
+
+/**
+ * Allows EventInstance content to be added to groups.
+ *
+ * @GroupContentEnabler(
+ *   id = "event_instance",
+ *   label = @Translation("Event Instance"),
+ *   description = @Translation("Adds Event Instance entities to groups."),
+ *   entity_type_id = "eventinstance",
+ *   path_key = "eventinstance",
+ * )
+ */
+class EventInstance extends GroupContentEnablerBase {
+}

src/Plugin/GroupContentEnabler/EventSeries.php

+<?php
+
+namespace Drupal\recurring_events\Plugin\GroupContentEnabler;
+
+use Drupal\group\Plugin\GroupContentEnablerBase;
+
+/**
+ * Allows EventSeries content to be added to groups.
+ *
+ * @GroupContentEnabler(
+ *   id = "event_series",
+ *   label = @Translation("Event Series"),
+ *   description = @Translation("Adds Event Series entities to groups."),
+ *   entity_type_id = "eventseries",
+ *   path_key = "eventseries",
+ * )
+ */
+class EventSeries extends GroupContentEnablerBase {
+}