Implement Policy for Required User Fields

[hifabienne]

As a administrator I want to be able to define which fields are required for my user.

Precondition for:
#4386

Acceptance Criteria

Beta Give feedback

1. I am able to define required user fields (Profile Information, Phone, excluding email and username because its always required)
2. I am able to call the api to get the policy
3. I am able to call the api to create the policy
4. I am able to call the api to update the policy

[hifabienne]

This issue will be closed in favor of #6433
As we will introduce user schemas in the future