HMS-2460 feat: update schema for domain reg token

- `POST /domains` is used by ipa-hcc to create a new domain. Response
  schema is reduced to domain_id and signing_keys.
- `PUT /domains/:uuid` is used by ipa-hcc to update domain
  information. Response schema is reduced to auto_enrollment_enabled
  state and signing_keys. Request does not take title, description, and
  enabled state.
- `PATCH /domains/:uuid` is used by users to update title, description,
  and auto_enrollment_enabled state. Other fields are not set.

The routes `/domains/:uuid/update` and `/domains/:uuid/register` as well
as unused schema elements been removed.

Signed-off-by: Christian Heimes <[email protected]>