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/examples/examples_test.py

@@ -6,12 +6,15 @@ import os
 import random
 
 from minio import Minio
+import psycopg
 import pytest
 
 from python_repositories.examples.artifact_object_repository import (
     ArtifactObjectRepository,
 )
 from python_repositories.examples.user_json_repository import UserJsonRepository
+from python_repositories.examples.user_table_repository import UserTableRepository
+from tests.integration.postgres._containers import TEST_TABLE
 
 pytestmark = [
     pytest.mark.integration,
@@ -36,6 +39,24 @@ def set_example_env(
         _ = os.environ.pop(key, default=None)
 
 
+@pytest.fixture(scope="module", autouse=True)
+def set_postgres_example_env(
+    postgres_container: str,
+    raw_postgres_client: psycopg.Connection,
+) -> Generator[None, None, None]:
+    """Set Postgres env vars for example repositories using from_env() defaults."""
+    env_vars = {
+        "POSTGRES_URI": postgres_container,
+        "POSTGRES_TABLE": TEST_TABLE,
+        "POSTGRES_PRIMARY_KEY": "id",
+    }
+    for key, value in env_vars.items():
+        os.environ[key] = value
+    yield
+    for key in env_vars:
+        _ = os.environ.pop(key, default=None)
+
+
 @pytest.fixture(scope="module")
 def user_data() -> Generator[dict[str, str], None, None]:
     """Provide sample user data for tests."""
@@ -77,3 +98,27 @@ def test_artifact_object_repository_store_and_get(
         assert received is not None
         artifact_data.seek(0)
         assert received.read() == artifact_data.read()
+
+
+@pytest.mark.needs_postgres
+def test_user_table_repository_save_and_get(
+    user_data: dict[str, str],
+) -> None:
+    """Test that UserTableRepository can save and retrieve a user."""
+    with UserTableRepository() as repo:
+        repo.save_user("alice", user_data)
+        user = repo.get_user("alice")
+        assert user is not None
+        assert user["name"] == user_data["name"]
+        assert user["email"] == user_data["email"]
+
+
+@pytest.mark.needs_postgres
+def test_user_table_repository_delete(
+    user_data: dict[str, str],
+) -> None:
+    """Test that UserTableRepository can delete a user."""
+    with UserTableRepository() as repo:
+        repo.save_user("alice", user_data)
+        repo.delete_user("alice")
+        assert repo.get_user("alice") is None