Add support for deleting phone-numbers or emails

[bendiknesbo]

Checklist

• I agree to the terms within the Auth0 Code of Conduct.

Describe the problem you'd like to have solved

With the recent addition of Connection Attributes, we would like to make a call to Management API to delete a user's phone-number or email. We can do that by sending a PATCH call to the users-endpoint (https://auth0.com/docs/api/management/v2/users/patch-users-by-id), with the payload {"phone_number":null} or {"email":null}.

However, there is no way to achieve this when using the Auth0 Go SDK, by using the function User.Update, since passing in a management.User with Email or PhoneNumber set to nil will marshal the struct to {}, which will not delete the phone/email.

Describe the ideal solution

Some suggestions:

• The management.User could be changed/extended to allow explicit null in the User.Update-call
• User.Update could take an option (e.g. option.DeletePhoneNumber(), option.DeleteEmail()) that would set the correct payload.
• A separate User.DeletePhone and User.DeleteEmail (and User.DeleteUsername also?) could be added, which would send the required payload.

Alternatives and current workarounds

A workaround is to use NewRequest and pass a payload that overrides the default Go marshalling, like:

type deletePhoneRequest struct{}
func (r deletePhoneRequest) MarshalJSON() ([]byte, error) {
	return []byte(`{"phone_number":null}`), nil
}

This requires us to manually handle the path to the PATCH-endpoint, and handling the status-code and closing of body, etc. manually.

Additional context

No response