Allow getAttr to return DN

Specify "DN" as attribute name to return, but will only work if not present in ldap.Entry.Attributes
Use when full DN is stored in groupSearch's userAttr

connector/ldap/ldap.go

@@ -47,6 +47,9 @@ import (
 //         baseDN: cn=groups,dc=example,dc=com
 //         filter: "(objectClass=group)"
 //         userAttr: uid
+//         # Use if full DN is needed and not available as any other attribute
+//         # Will only work if "DN" attribute does not exist in the record
+//         # userAttr: DN
 //         groupAttr: member
 //         nameAttr: name
 //
@@ -285,6 +288,9 @@ func getAttr(e ldap.Entry, name string) string {
 		}
 		return a.Values[0]
 	}
+	if name == "DN" {
+		return e.DN
+	}
 	return ""
 }