Modules
Row-level security as the adapter: the rules are Postgres policies on the tables themselves.
The repo, the schemas, and the migrations table that Mediate.Postgres
needs beyond the configuration.
What the database says its own rules are.
Declared-fact coverage for row-level security: every column the policies read is a declared fact.
The helpers a migration calls. This is the only place the package writes DDL. Every statement runs through the repo the caller passes, under the library exemption, so the seam mediates a migration like any other call.
One row-level security policy as pg_policy holds it. It holds the name,
the table, the command it applies to, and the USING and WITH CHECK
expressions as the database renders them.
The policy version of row-level security: the migration number.