New python-fastapi generator (#9611)

* [python-fastapi] Added new generator

See https://fastapi.tiangolo.com/ for more details about FastAPI

Signed-off-by: Nikita Vakula <programmistov.programmist@gmail.com>

* [python-fastapi] Added samples

Signed-off-by: Nikita Vakula <programmistov.programmist@gmail.com>

samples/server/petstore/python-fastapi/tests/conftest.py

@@ -0,0 +1,20 @@
+import contextlib
+from typing import Any
+
+import pytest
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+
+from openapi_server.main import app as application
+
+
+@pytest.fixture
+def app() -> FastAPI:
+    application.dependency_overrides = {}
+
+    return application
+
+
+@pytest.fixture
+def client(app) -> TestClient:
+    return TestClient(app)