Callbacks service docs updated

interface/models/auth/login_data.yaml

@@ -1,6 +1,7 @@
 components:
   schemas:
     LoginData:
+      description: Credentials and optional locale used during user sign-in.
       type: object
       additionalProperties: false
       required:
@@ -8,10 +9,13 @@ components:
         - password
       properties:
         login:
+          description: User login identifier, represented as an email address.
           type: string
           format: email
         password:
+          description: User password submitted for authentication.
           type: string
           format: password
         locale:
+          description: Optional locale preference provided at login time.
           type: string