non-jira: comment about usage of ldap login attribute config

src/main/resources/serviceconfig/olat.properties

@@ -935,7 +935,8 @@ ldap.attributename.useridentifyer=sAMAccountName
 ldap.attributename.email=mail
 ldap.attributename.firstName=givenName
 ldap.attributename.lastName=sn
-# attribute used as username to log in
+# Attribute used as username to log in. Note: the configured login attribute MUST be one of the mapped attributes below, e.g. genericTextProperty1 
+# If the login attribute should not be visible in OO, then disable the OO user property in all contexts. 
 ldap.login.attribute=${ldap.attributename.useridentifyer}
 #mappings from ldap-attrib to olat-userproperty
 ldap.attrib.gen.map.ldapkey1=