For Horizon: designate_policy.json needs to be simpler to work

[Leandro Reox]

If you are just a member of a tenant, with the role _member_ on it, if you use the policy.json that ships with the API, horizon is not going to show to the user all the buttons to

- create domains
- manage records

In order to allow this, the designate_policy.json that we put to horizon has to have simpler rules, for example:

change:

"create_domain": "rule:admin_or_owner",

to:

"create_domain": "role:_member_",