Correct enterprise attributes feature to domain_verification

What does this MR do and why?

This is a follow-up MR based on the feedback: !125764 (comment 1470281283) to correct the feature associated with the enterprise users API.

How to set up and validate locally

Select any user and manually update the enterprise attributes (enterprise_group_id, enterprise_group_associated_at) using the console:

user= User.find(5)
user.user_detail.update(enterprise_group_id: 33, enterprise_group_associated_at: Time.now)

Use the API endpoint api/v4/users/ID. You will observe that the response now includes the enterprise attributes.

Example:

http://localhost:3000/api/v4/users/5

{"id":5,"username":"arnetta","name":"Cameron 
"enterprise_group_id":35,
"enterprise_group_associated_at":"2023-07-05T11:23:59.042Z",
"trial":false}

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.