feat: move db related function from pytest to db module (#119)

docs/module/db.md

@@ -87,6 +87,33 @@ await wait_for_row_change(
 )
 ```
 
+## Creating a database
+
+[`create_database`](../reference/db.md#fastapi_toolsets.db.create_database) creates a database at a given URL. It connects to *server_url* and issues a `CREATE DATABASE` statement:
+
+```python
+from fastapi_toolsets.db import create_database
+
+SERVER_URL = "postgresql+asyncpg://postgres:postgres@localhost/postgres"
+
+await create_database(db_name="myapp_test", server_url=SERVER_URL)
+```
+
+For test isolation with automatic cleanup, use [`create_worker_database`](../reference/pytest.md#fastapi_toolsets.pytest.utils.create_worker_database) from the `pytest` module instead — it handles drop-before, create, and drop-after automatically.
+
+## Cleaning up tables
+
+[`cleanup_tables`](../reference/db.md#fastapi_toolsets.db.cleanup_tables) truncates all tables:
+
+```python
+from fastapi_toolsets.db import cleanup_tables
+
+@pytest.fixture(autouse=True)
+async def clean(db_session):
+    yield
+    await cleanup_tables(session=db_session, base=Base)
+```
+
 ---
 
 [:material-api: API Reference](../reference/db.md)