feat(P01): TASK-01-04..07 Postgres DB foundation — migrate + schema + PgStore + tests
- db/pg_migrate.py: asyncpg migration runner with _pg_migrations tracking
table, ordered .sql, transactional, 3x retry on connection failure (R-MT-02).
- db/pg_schema.sql + db/pg_migrations/0001_operator_tier.sql: 5 operator-tier
tables (operators, issued_credentials, mastery_gate_events,
cohort_aggregates, issuer_keys) using gen_random_uuid() (PG16 core, no
extension). cohort_aggregates is a plain table, NOT partitioned (D-050).
- db/pg_store.py: PgStore class implementing the IssuerKeyStore protocol
(init/get_active/get_public_key_row/set_superseded) plus operator CRUD,
cohort aggregate read/write, credential methods, gate events.
get_public_key_row queries by id (not status) → finds superseded keys
(R-VC-MIG-01 verification fallback, D-051). No cross-DB FKs (D-031).
- tests/test_pg_store.py: 13 integration tests (skip if PRAXIS_PG_DSN unset).
---ci---
project: praxis
phase: 1
milestone: v0.4
status: execute
persona: data-engineer
task: 01-04,01-05,01-06,01-07
requirements:
covered: [REQ-MT-01, REQ-NFR-MT-01, REQ-MT-02]
---/ci---
Praxis CI
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