Testing Site URL: https://gh-imp-2022-00145.castlecraft.co.in
Pull Request URL: https://github.com/frappe/frappe/pull/15630
Pull Request Title: fix(ldap): using `ldap_group_objectclass` instead of `ldap_group_mappings_section` field for validating custom config
Pull Request Description:
Bug introduced by #13777.
Causing the LDAP Settings using Custom Directory Server to not save successfully. Because the ldapgroupmappings_section variable will never be set and the validate function will fail.
Re of https://github.com/frappe/frappe/pull/15541