LDAP: Add enum request with custom connection This commit changes the enumerate-sdap-domain request to accept a connection context per object that can be enumerated. Internally in the request, an sdap_id_op is also created per enumerated object type. This change will allow i.e. users to be enumerated using GC connection, while keeping the LDAP connection for groups and services.

LDAP: Move the ldap enum request to its own reusable module The LDAP enumeration was too closely tied to the LDAP identity provider. Because some providers might need special handling such as refresh the master domain record before proceeding with the enumeration itself, this patch splits the request itself to a separate async request and lets the ldap_id_enum.c module only configure this new request. Also move the enum timestamp to sdap_domain to make the enum tracking per sdap domain. The cleanup timestamp will be moved in another patch.