server: Add modifyTimestamp and pwdChangedTime attributes (#1265)

Add a modifyTimestamp attribute to LDAP entries for users and groups, and expose pwdChangedTime for users.
These attributes let clients track when an entry (or its password) was last changed.

 -  modifyTimestamp is a server-maintained attribute that updates on any write to user or group entries, including membership changes (on the group side).

 -  pwdChangedTime is set when a user’s password is created or changed.

crates/sql-backend-handler/src/sql_group_backend_handler.rs

@@ -206,6 +206,7 @@ impl GroupBackendHandler for SqlBackendHandler {
             lowercase_display_name: Set(lower_display_name),
             creation_date: Set(now),
             uuid: Set(uuid),
+            modified_date: Set(now),
             ..Default::default()
         };
         Ok(self
@@ -268,10 +269,12 @@ impl SqlBackendHandler {
             .display_name
             .as_ref()
             .map(|s| s.as_str().to_lowercase());
+        let now = chrono::Utc::now().naive_utc();
         let update_group = model::groups::ActiveModel {
             group_id: Set(request.group_id),
             display_name: request.display_name.map(Set).unwrap_or_default(),
             lowercase_display_name: lower_display_name.map(Set).unwrap_or_default(),
+            modified_date: Set(now),
             ..Default::default()
         };
         update_group.update(transaction).await?;