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/unit/postgres_config_test.py

@@ -0,0 +1,69 @@
+"""Unit tests for PostgresConfig."""
+
+from __future__ import annotations
+
+import pytest
+
+from python_repositories.config import PostgresConfig
+
+
+def _set_required_postgres_env(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setenv("POSTGRES_URI", "postgresql://localhost/mydb")
+    monkeypatch.setenv("POSTGRES_TABLE", "users")
+
+
+def test_from_env_loads_all_fields(monkeypatch: pytest.MonkeyPatch) -> None:
+    _set_required_postgres_env(monkeypatch)
+    config = PostgresConfig.from_env(use_dotenv=False)
+    assert config.uri == "postgresql://localhost/mydb"
+    assert config.table == "users"
+    assert config.primary_key == "id"
+
+
+def test_from_env_reads_primary_key_from_env(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    _set_required_postgres_env(monkeypatch)
+    monkeypatch.setenv("POSTGRES_PRIMARY_KEY", "user_id")
+    config = PostgresConfig.from_env(use_dotenv=False)
+    assert config.primary_key == "user_id"
+
+
+def test_from_env_defaults_primary_key_to_id_when_unset(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    _set_required_postgres_env(monkeypatch)
+    monkeypatch.delenv("POSTGRES_PRIMARY_KEY", raising=False)
+    config = PostgresConfig.from_env(use_dotenv=False)
+    assert config.primary_key == "id"
+
+
+def test_from_env_raises_when_uri_missing(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.delenv("POSTGRES_URI", raising=False)
+    monkeypatch.setenv("POSTGRES_TABLE", "users")
+    with pytest.raises(Exception):
+        PostgresConfig.from_env(use_dotenv=False)
+
+
+def test_from_env_raises_when_table_missing(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setenv("POSTGRES_URI", "postgresql://localhost/mydb")
+    monkeypatch.delenv("POSTGRES_TABLE", raising=False)
+    with pytest.raises(Exception):
+        PostgresConfig.from_env(use_dotenv=False)
+
+
+def test_from_env_respects_custom_env_var_names(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    monkeypatch.setenv("CUSTOM_POSTGRES_URI", "postgresql://custom/mydb")
+    monkeypatch.setenv("CUSTOM_POSTGRES_TABLE", "items")
+    monkeypatch.setenv("CUSTOM_POSTGRES_PRIMARY_KEY", "item_id")
+    config = PostgresConfig.from_env(
+        "CUSTOM_POSTGRES_URI",
+        "CUSTOM_POSTGRES_TABLE",
+        "CUSTOM_POSTGRES_PRIMARY_KEY",
+        use_dotenv=False,
+    )
+    assert config.uri == "postgresql://custom/mydb"
+    assert config.table == "items"
+    assert config.primary_key == "item_id"