The user's permission of a domain.

| Enums ||
|---|---|
| `PERMISSION_UNSPECIFIED` | Unspecified permission. |
| `READER` | User has read access to the domain. |
| `ADMIN` | User has admin access to the domain. |
| `OWNER` | User has owner access to the domain. |
| `NONE` | User has no access to the domain. |