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 <cursoragent@cursor.com>

tests/unit/adapters_test.py

@@ -45,6 +45,7 @@ from python_repositories import JsonRepositoryInterface
 assert JsonRepositoryInterface is not None
 assert "python_repositories.adapters.redis_adapter" not in sys.modules
 assert "python_repositories.adapters.minio_adapter" not in sys.modules
+assert "python_repositories.adapters.postgres_adapter" not in sys.modules
 """
     result = subprocess.run(
         [sys.executable, "-c", script],
@@ -58,10 +59,11 @@ assert "python_repositories.adapters.minio_adapter" not in sys.modules
 
 def test_lazy_adapter_load_succeeds_when_extra_present() -> None:
     """Adapters load when their optional dependencies are installed."""
-    from python_repositories import MinioAdapter, RedisAdapter
+    from python_repositories import MinioAdapter, PostgresAdapter, RedisAdapter
 
     assert RedisAdapter.__name__ == "RedisAdapter"
     assert MinioAdapter.__name__ == "MinioAdapter"
+    assert PostgresAdapter.__name__ == "PostgresAdapter"
 
 
 def test_redis_adapter_import_error_without_extra() -> None:
@@ -86,6 +88,17 @@ def test_minio_adapter_import_error_without_extra() -> None:
     importlib.reload(minio_adapter_module)
 
 
+def test_postgres_adapter_import_error_without_extra() -> None:
+    """Missing postgres extra raises ImportError with install hint."""
+    import python_repositories.adapters.postgres_adapter as postgres_adapter_module
+
+    with patch.object(builtins, "__import__", new=_block_backend_import("psycopg")):
+        with pytest.raises(ImportError, match=r"python-repositories\[postgres\]"):
+            importlib.reload(postgres_adapter_module)
+
+    importlib.reload(postgres_adapter_module)
+
+
 def test_top_level_lazy_import_propagates_redis_import_error() -> None:
     """Top-level RedisAdapter access surfaces adapter import errors."""
     with patch(
@@ -112,6 +125,19 @@ def test_top_level_lazy_import_propagates_minio_import_error() -> None:
             _ = python_repositories.MinioAdapter
 
 
+def test_top_level_lazy_import_propagates_postgres_import_error() -> None:
+    """Top-level PostgresAdapter access surfaces adapter import errors."""
+    with patch(
+        "importlib.import_module",
+        side_effect=ImportError(
+            "Postgres support requires the postgres extra. "
+            "Install with: pip install python-repositories[postgres]"
+        ),
+    ):
+        with pytest.raises(ImportError, match=r"python-repositories\[postgres\]"):
+            _ = python_repositories.PostgresAdapter
+
+
 def test_adapters_subpackage_lazy_import_succeeds() -> None:
     """Adapter subpackage imports delegate to the same lazy loader."""
     from python_repositories.adapters import RedisAdapter
@@ -123,7 +149,7 @@ def test_adapters_dir_exposes_lazy_exports() -> None:
     """dir(adapters) includes lazy adapter names for tab completion."""
     import python_repositories.adapters as adapters
 
-    assert {"RedisAdapter", "MinioAdapter"}.issubset(set(dir(adapters)))
+    assert {"RedisAdapter", "MinioAdapter", "PostgresAdapter"}.issubset(set(dir(adapters)))
 
 
 def test_adapters_getattr_raises_for_unknown() -> None:
@@ -138,3 +164,4 @@ def test_top_level_dir_exposes_lazy_exports() -> None:
     """dir(python_repositories) includes lazy adapter names for tab completion."""
     assert "RedisAdapter" in dir(python_repositories)
     assert "MinioAdapter" in dir(python_repositories)
+    assert "PostgresAdapter" in dir(python_repositories)