fix: make "login_name" field optional for API edit user (#38917)

templates/swagger/v1-swagger.generated.json

@@ -27879,7 +27879,6 @@
         "login_name": {
           "description": "identifier of the user, provided by the external authenticator (if configured)",
           "type": "string",
-          "default": "empty",
           "x-go-name": "LoginName"
         },
         "must_change_password": {
@@ -29124,8 +29123,7 @@
       "description": "EditUserOption edit user options",
       "type": "object",
       "required": [
-        "source_id",
-        "login_name"
+        "source_id"
       ],
       "properties": {
         "active": {
@@ -29177,7 +29175,6 @@
         "login_name": {
           "description": "identifier of the user, provided by the external authenticator (if configured)",
           "type": "string",
-          "default": "empty",
           "x-go-name": "LoginName"
         },
         "max_repo_creation": {
@@ -33551,7 +33548,6 @@
         "login_name": {
           "description": "identifier of the user, provided by the external authenticator (if configured)",
           "type": "string",
-          "default": "empty",
           "x-go-name": "LoginName"
         },
         "prohibit_login": {