Runs a multi-statement SQL script against the admin pool via the simple
query protocol. Executed against the shared pool reference (not a
&mut PgConnection) so the future stays Send/spawnable — the &mut
executor form trips a higher-ranked-lifetime bound once boot() is spawned.
Runs the full migration set against the database at url. Used by
provisioning to bring a freshly-created per-user database up to the
(DDL-only) schema.
True when the current thread has installed a test pool. Used by
User::get_connection to choose between the test override and the
per-user production pool.