LDAP group sync should treat group CN case-insensitively
Currently if a LdapGroupLink is created with a
cn whose case does not match the LDAP server's attribute, group membership evaluation will not find any member of the group.
GitLab should (probably) treat group cn case-insensitively as it does for user uid. The case-sensitivity is believed to come from this single line (at time of writing).
We could provide a fix together with our proposal for #278