[FIX] fastapi: support both starlette < and >= 0.48

Starting from `starlette >= 0.48`, the `status.HTTP_422_UNPROCESSABLE_ENTITY`
emits a deprecation warning, as it has been replaced by
`status.HTTP_422_UNPROCESSABLE_CONTENT`.

To be compatible with past and future versions, we simply use the integer value
`422`, aligning also with the updated `fastapi` documentation:

See:
- fastapi/fastapi#14077

Author: ivantodorovich

fastapi/error_handlers.py

@@ -29,7 +29,10 @@ def convert_exception_to_status_body(exc: Exception) -> tuple[int, dict]:
         status_code = exc.status_code
         details = exc.detail
     elif isinstance(exc, RequestValidationError):
-        status_code = status.HTTP_422_UNPROCESSABLE_CONTENT
+        # Use integer status code to supress starlette >= 0.48 deprecation warning
+        # See: https://github.com/fastapi/fastapi/pull/14077
+        # status_code = status.HTTP_422_UNPROCESSABLE_CONTENT
+        status_code = 422
         details = jsonable_encoder(exc.errors())
     elif isinstance(exc, WebSocketRequestValidationError):
         status_code = status.WS_1008_POLICY_VIOLATION

fastapi/tests/test_fastapi.py

@@ -156,9 +156,7 @@ def test_request_validation_error(self) -> None:
             route = "/fastapi_demo/demo/exception?exception_type=BAD&error_message="
             response = self.url_open(route, timeout=200)
             mocked_commit.assert_not_called()
-            self.assertEqual(
-                response.status_code, status.HTTP_422_UNPROCESSABLE_CONTENT
-            )
+            self.assertEqual(response.status_code, 422)
 
     def test_no_commit_on_exception(self) -> None:
         # this test check that the way we mock the cursor is working as expected