Add documentation for pending members API endpoint

doc/api/members.md

@@ -634,6 +634,65 @@ Example request:
 curl --request POST --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/api/v4/groups/:id/members/approve_all"
 ```
 
+## List pending members of a group and its subgroups and projects
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/332596) in GitLab 14.6.
+
+For a group and its subgroups and projects, get a list of all members in an `awaiting` state and those who are invited but do not have a GitLab account.
+
+This request returns all matching group and project members from all groups and projects in the root group's hierarchy.
+
+When the member is an invited user that has not signed up for a GitLab account yet, the invited email address is returned.
+
+This API endpoint works on top-level groups only. It does not work on subgroups.
+
+This API endpoint requires permission to administer members for the group.
+
+This API endpoint takes [pagination](index.md#pagination) parameters `page` and `per_page` to restrict the list of members.
+
+```plaintext
+GET /groups/:id/pending_members
+```
+
+| Attribute | Type | Required | Description |
+| --------- | ---- | -------- | ----------- |
+| `id`      | integer/string | yes | The ID or [URL-encoded path of the group](index.md#namespaced-path-encoding) owned by the authenticated user |
+
+```shell
+curl --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/api/v4/groups/:id/pending_members"
+```
+
+Example response:
+
+```json
+[
+  {
+    "id": 168,
+    "name": "Alex Garcia",
+    "username": "alex_garcia",
+    "email": "alex@example.com",
+    "avatar_url": "http://example.com/uploads/user/avatar/1/cd8.jpeg",
+    "web_url": "http://example.com/alex_garcia",
+    "approved": false,
+    "invited": false
+  },
+  {
+    "id": 169,
+    "email": "sidney@example.com",
+    "avatar_url": "http://gravatar.com/../e346561cd8.jpeg",
+    "approved": false,
+    "invited": true
+  },
+  {
+    "id": 170,
+    "email": "zhang@example.com",
+    "avatar_url": "http://gravatar.com/../e32131cd8.jpeg",
+    "approved": true,
+    "invited": true
+  }
+]
+```
+
 ## Give a group access to a project
 
 See [share project with group](projects.md#share-project-with-group)