CiviLDAP provides LDAP authentication for Gitlab based on civicrm.org logins. In the past, it also provided LDAP authentication to JIRA and Confluence.
The service runs on www-prod-2.civicrm.org.
Gitlab issues should be tagged with ldap (although it also includes the ssh LDAP service, which is a separate service running off OpenLDAP).
More documentation: https://lab.civicrm.org/infrastructure/ops/blob/master/ldap-websites.md