Include login_name in adminCreateUser response (#20283)

`login_name` (Authentication Sign-in Name) is not included in the response of `adminUserCreate` API. 
This PR is to return user-specified `login_name` if there is one.

templates/swagger/v1_json.tmpl

@@ -18487,6 +18487,12 @@
           "type": "string",
           "x-go-name": "UserName"
         },
+        "login_name": {
+          "description": "the user's authentication sign-in name.",
+          "type": "string",
+          "default": "empty",
+          "x-go-name": "LoginName"
+        },
         "prohibit_login": {
           "description": "Is user login prohibited",
           "type": "boolean",