Merge branch 'bprescott/docs/20220112-deleteuser' into 'master'

null constraint issue when deleting users

See merge request gitlab-org/gitlab!78055

doc/user/profile/account/delete_account.md

@@ -82,14 +82,21 @@ is a sole owner of. Administrators can also request this behavior when
 deleting users from the [API](../../../api/users.md#user-deletion) or the
 Admin Area.
 
-<!-- ## Troubleshooting
+## Troubleshooting
 
-Include any troubleshooting steps that you can foresee. If you know beforehand what issues
-one might have when setting this up, or when something is changed, or on upgrading, it's
-important to describe those, too. Think of things that may go wrong and include them here.
-This is important to minimize requests for support, and to avoid doc comments with
-questions that you know someone might ask.
+### Deleting a user results in a PostgreSQL null value error
 
-Each scenario can be a third-level heading, e.g. `### Getting error message X`.
-If you have none to add when creating a doc, leave this section in place
-but commented out to help encourage others to add to it in the future. -->
+There is [a known issue](https://gitlab.com/gitlab-org/gitlab/-/issues/349411) that results
+in users not being deleted, and the following error generated:
+
+```plaintext
+ERROR: null value in column "user_id" violates not-null constraint
+```
+
+The error can be found in the [PostgreSQL log](../../../administration/logs.md#postgresql-logs) and
+in the **Retries** section of the [background jobs view](../../admin_area/index.md#background-jobs) in the Admin Area.
+
+If the user being deleted used the [iterations](../../group/iterations/index.md) feature, such
+as adding an issue to an iteration, you must use
+[the workaround documented in the issue](https://gitlab.com/gitlab-org/gitlab/-/issues/349411#workaround)
+to delete the user.