feat: add app factory with health endpoint and test infrastructure

tests/conftest.py

@@ -0,0 +1,20 @@
+from collections.abc import AsyncIterator
+
+import pytest
+from httpx import ASGITransport, AsyncClient
+
+from fastapi_oidc_op.app import create_app
+from fastapi_oidc_op.config import Settings
+
+
+@pytest.fixture
+def settings() -> Settings:
+    return Settings(issuer="http://localhost:8000")
+
+
+@pytest.fixture
+async def client(settings: Settings) -> AsyncIterator[AsyncClient]:
+    app = create_app(settings)
+    transport = ASGITransport(app=app)
+    async with AsyncClient(transport=transport, base_url=settings.issuer) as ac:
+        yield ac