V14: fix user set user group endpoint

[Zeegaan]

Notes

• Fixes the umbraco/management/api/v1/user/set-user-groups, as it did not know how to map success status code (we didn't check for succeed first)
• Refactored a few methods to use attempt so it lines up with the rest of the API 👍

How to test

• Use the umbraco/management/api/v1/user/set-user-groups, to set groups for a user
• It should now work