Add Postgres table adapter with TableRepositoryInterface.

Introduce PostgresAdapter for dict-based row CRUD via psycopg3, including config, lazy exports, unit/integration tests with testcontainers, and an example UserTableRepository.

Co-authored-by: Cursor <[email protected]>

tests/integration/postgres/_containers.py

@@ -0,0 +1,76 @@
+"""Postgres container session helpers for integration tests."""
+
+from collections.abc import Generator
+
+import psycopg
+from psycopg.rows import dict_row
+from testcontainers.postgres import PostgresContainer
+
+from python_repositories.config import PostgresConfig
+
+POSTGRES_IMAGE = "postgres:16"
+TEST_TABLE = "test_items"
+
+
+_postgres_uri: str | None = None
+_postgres_container: PostgresContainer | None = None
+_raw_postgres_client: psycopg.Connection | None = None
+_postgres_uri_refs = 0
+_raw_postgres_client_refs = 0
+
+
+def postgres_uri() -> Generator[str, None, None]:
+    """Yield a session-scoped Postgres URI, starting the container once."""
+    global _postgres_uri, _postgres_container, _postgres_uri_refs
+    if _postgres_uri is None:
+        _postgres_container = PostgresContainer(POSTGRES_IMAGE, driver=None)
+        _postgres_container.start()
+        _postgres_uri = _postgres_container.get_connection_url()
+
+    _postgres_uri_refs += 1
+    yield _postgres_uri
+    _postgres_uri_refs -= 1
+
+    if _postgres_uri_refs == 0 and _postgres_container is not None:
+        _postgres_container.stop()
+        _postgres_container = None
+        _postgres_uri = None
+
+
+def postgres_config_from_container(uri: str) -> PostgresConfig:
+    """Build PostgresConfig from a container URI."""
+    return PostgresConfig(uri=uri, table=TEST_TABLE, primary_key="id")
+
+
+def raw_postgres_client_from_container(
+    uri: str,
+) -> Generator[psycopg.Connection, None, None]:
+    """Yield a session-scoped raw Postgres client, reusing one client per session."""
+    global _raw_postgres_client, _raw_postgres_client_refs
+    if _raw_postgres_client is None:
+        _raw_postgres_client = psycopg.connect(
+            uri,
+            row_factory=dict_row,  # type: ignore[arg-type]
+            autocommit=True,
+        )
+        with _raw_postgres_client.cursor() as cursor:
+            cursor.execute(
+                f"""
+                CREATE TABLE IF NOT EXISTS {TEST_TABLE} (
+                    id TEXT PRIMARY KEY,
+                    name TEXT NOT NULL,
+                    value INTEGER,
+                    email TEXT
+                )
+                """
+            )
+
+    _raw_postgres_client_refs += 1
+    yield _raw_postgres_client
+    _raw_postgres_client_refs -= 1
+
+    if _raw_postgres_client_refs == 0 and _raw_postgres_client is not None:
+        with _raw_postgres_client.cursor() as cursor:
+            cursor.execute(f"TRUNCATE TABLE {TEST_TABLE}")
+        _raw_postgres_client.close()
+        _raw_postgres_client = None