# Practice domain belongs to the tenant, not only to the clinic

`practice_domain_id` originally lived on `clinics`, but every piece of operational data in this
codebase is owned by an `(entity_type, entity_id)` pair where `entity_type` is `doctor` or `clinic`.
A solo practice is a `doctor` tenant, so it could never declare a practice domain at all — the beauty
domain has the same hole, it simply had not been noticed. The column is therefore added to `doctors`
as well and read through a single `PracticeDomainResolver` that takes an `EntityContext`, so no
caller has to know which kind of tenant it is looking at.

## Considered Options

Letting a doctor inherit the domain of a clinic they work at was rejected: a doctor with no clinic
would stay domainless, and a doctor working at two clinics with different domains would be ambiguous.