Update documentation.

src/PermissionManagerInterface.php

@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types = 1);
+
 namespace Drupal\og;
 
 /**
@@ -21,7 +23,7 @@ interface PermissionManagerInterface {
    * @param array $group_content_bundle_ids
    *   An array of group content bundle IDs, keyed by group content entity type
    *   ID.
-   * @param string $role_name
+   * @param string|null $role_name
    *   Optional default role name to filter the permissions on. If omitted, all
    *   permissions will be returned.
    *
@@ -33,14 +35,23 @@ public function getDefaultPermissions($group_entity_type_id, $group_bundle_id, a
   /**
    * Returns permissions that are enabled by default for the given role.
    *
-   * This returns group level permissions such as 'subscribe without approval'
-   * and 'administer group'.
+   * This returns the group level permissions that are populated by default when
+   * a new group is created. For example the 'manage members' permission is
+   * granted by default to the administrator role, and the 'subscribe'
+   * permission to the anonymous role.
+   *
+   * New default permissions can be added by creating an event listener for the
+   * PermissionEvent. The default permissions that ship with Organic Groups can
+   * be found in OgEventSubscriber::provideDefaultOgPermissions().
+   *
+   * @see \Drupal\og\Event\PermissionEventInterface
+   * @see \Drupal\og\EventSubscriber\OgEventSubscriber::provideDefaultOgPermissions()
    *
    * @param string $group_entity_type_id
    *   The entity type ID of the group for which to return permissions.
    * @param string $group_bundle_id
    *   The bundle ID of the group for which to return permissions.
-   * @param string $role_name
+   * @param string|null $role_name
    *   Optional default role name to filter the permissions on. If omitted, all
    *   permissions will be returned.
    *
@@ -55,14 +66,23 @@ public function getDefaultGroupPermissions($group_entity_type_id, $group_bundle_
    * This returns group content entity operation permissions such as 'edit own
    * article content'.
    *
+   * New default group content entity operation permissions can be added by
+   * creating an event listener for the PermissionEvent. The default group
+   * content operation permissions that ship with Organic Groups can be found in
+   * OgEventSubscriber.
+   *
+   * @see \Drupal\og\Event\PermissionEventInterface
+   * @see \Drupal\og\EventSubscriber\OgEventSubscriber::provideDefaultNodePermissions()
+   * @see \Drupal\og\EventSubscriber\OgEventSubscriber::getDefaultEntityOperationPermissions()
+   *
    * @param string $group_entity_type_id
    *   The entity type ID of the group for which to return permissions.
    * @param string $group_bundle_id
    *   The bundle ID of the group for which to return permissions.
    * @param array $group_content_bundle_ids
    *   An array of group content bundle IDs, keyed by group content entity type
    *   ID.
-   * @param string $role_name
+   * @param string|null $role_name
    *   Optional default role name to filter the permissions on. If omitted, all
    *   permissions will be returned.
    *