Expose membership_lock on group detail API

Changelog: changed
EE: true

doc/api/groups.md

@@ -483,6 +483,8 @@ Example response:
 
 ## Details of a group
 
+> The `membership_lock` field was [added](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/82271) in GitLab 14.10.
+
 Get all details of a group. This endpoint can be accessed without authentication
 if the group is publicly accessible. In case the user that requests is an administrator
 if the group is publicly accessible. With authentication, it returns the `runners_token`
@@ -715,6 +717,18 @@ the `marked_for_deletion_on` attribute:
 }
 ```
 
+Users of [GitLab Premium or higher](https://about.gitlab.com/pricing/) also see
+the `membership_lock` attribute:
+
+```json
+{
+  "id": 4,
+  "description": "Aliquid qui quis dignissimos distinctio ut commodi voluptas est.",
+  "membership_lock": false,
+  ...
+}
+```
+
 When adding the parameter `with_projects=false`, projects aren't returned.
 
 ```shell

ee/lib/ee/api/entities/group_detail.rb

@@ -11,6 +11,8 @@ module EE
           expose :extra_shared_runners_minutes_limit
           expose :prevent_forking_outside_group?,
                  as: :prevent_forking_outside_group
+          expose :membership_lock?,
+                 as: :membership_lock
         end
       end
     end