Add notes for the user creation feature

docs/auth.md

@@ -132,4 +132,6 @@ Note that you need to be logged in using a user with a role that has creating us
 
 Additionally, it's important to note that the `/api/tables/_users/rows/` endpoint functions slightly differently compared to other `/api/tables/<table_name>/rows/` endpoints. When creating or updating user data through this endpoint, we need to provide the raw passwords, which are then automatically hashed before being stored in the `_hashed_password` field. This extra step enhances the security of the stored passwords.
 
+When creating a user, the required fields are `username` and `password`. However, you also have the flexibility to include additional optional fields. To do this, you will need to modify the schema of the `_users` table in your database using a suitable database editor GUI tool. Simply add the desired field(s) to the database schema for the `_users` table. Once the schema is updated, you can pass the optional field(s) from your client application during user creation.
+
 Furthermore, when retrieving user data, the endpoint automatically filters out sensitive information such as the `_hashed_password` and `_salt` fields. This precautionary measure is in place to address security concerns and ensure that only necessary and non-sensitive information is included in the returned results.