Use LDAP Modify Password ExtOp for updating passwords

By default the graph API will now use the LDAP Password Modify Extended
Operation for setting user passwords. By this we make sure that the
LDAP server can e.g. properly hash the password with and algorithm that
it supports.

This can be reverted to the old behaviour (using "normal" LDAP modify
requests) by setting GRAPH_LDAP_SERVER_USE_PASSWORD_MODIFY_EXOP=false

Fixes: #3778

services/graph/pkg/config/defaults/defaultconfig.go

@@ -46,6 +46,7 @@ func DefaultConfig() *config.Config {
 				CACert:                   path.Join(defaults.BaseDataPath(), "idm", "ldap.crt"),
 				BindDN:                   "uid=libregraph,ou=sysusers,o=libregraph-idm",
 				UseServerUUID:            false,
+				UsePasswordModExOp:       true,
 				WriteEnabled:             true,
 				UserBaseDN:               "ou=users,o=libregraph-idm",
 				UserSearchScope:          "sub",