Update user documentation

doc/api/settings.md

@@ -421,6 +421,7 @@ listed in the descriptions of the relevant settings.
 | `unique_ips_limit_per_user`              | integer          | required by: `unique_ips_limit_enabled` | Maximum number of IPs per user. |
 | `unique_ips_limit_time_window`           | integer          | required by: `unique_ips_limit_enabled` | How many seconds an IP is counted towards the limit. |
 | `usage_ping_enabled`                     | boolean          | no                                   | Every week GitLab reports license usage back to GitLab, Inc. |
+| `user_deactivation_emails_enabled`       | boolean          | no                                   | Send an email to users upon account deactivation. |
 | `user_default_external`                  | boolean          | no                                   | Newly registered users are external by default. |
 | `user_default_internal_regex`            | string           | no                                   | Specify an email address regex pattern to identify default internal users. |
 | `user_oauth_applications`                | boolean          | no                                   | Allow users to register any application to use GitLab as an OAuth provider. |

doc/user/admin_area/moderate_users.md

@@ -153,6 +153,9 @@ For the deactivation option to be visible to an admin, the user:
 NOTE:
 Users can also be deactivated using the [GitLab API](../../api/users.md#deactivate-user).
 
+NOTE:
+Users can be notified about account deactivation if [user deactivation emails](settings/email.md#enable-user-deactivation-emails) are enabled.
+
 ### Automatically deactivate dormant users
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/320875) in GitLab 14.0.

doc/user/admin_area/settings/email.md

@@ -72,6 +72,18 @@ To add additional text to emails:
 1. Enter your text in the **Additional text** field.
 1. Select **Save changes**.
 
+## Enable user deactivation emails **(FREE SELF)**
+
+GitLab can send email notifications to users when their account has been deactivated.
+
+To enable these notifications:
+
+1. On the top bar, select **Menu > Admin**.
+1. On the left sidebar, select **Settings > Preferences** (`/admin/application_settings/preferences`).
+1. Expand **Email**.
+1. Select **Enable user deactivation emails**.
+1. Select **Save changes**.
+
 <!-- ## Troubleshooting
 
 Include any troubleshooting steps that you can foresee. If you know beforehand what issues