HttpContextAccessor.HttpContext for a $batch request becomes unset after returning from ODataBatchMiddleware

(Related to Issue #230 )

Problem Statement

In any middleware that is in the pipeline above the ODataBatchMiddleware HttpContextAccessor.HttpContext will be populated before the request is passed onto the batch middleware but will be unset after returning from the batch middleware. We expect the HttpContextAccessor.HttpContext to be populated at all times.

How to reproduce

We have a minimal proof-of-concept example set up here to demonstrate this issue (you can just pull the project and build to the solution to test, no other dependencies required). Please ping me if you have an issue accessing this. The particular point of demonstration is here.

1. Clone to repository
2. Open the .sln and run the ODataBatchHttpContext service
3. Make the following $batch request against the service (using ARC/Postman/Fiddler etc.)

URI:
POST http://localhost:5000/api/$batch

Headers:

Content-Type: multipart/mixed; boundary=batch_aaf78fdf-f309-4c1d-ab0f-3c317770e5c6

Body:

--batch_aaf78fdf-f309-4c1d-ab0f-3c317770e5c6
Content-Type: application/http
Content-Transfer-Encoding: binary

GET  http://localhost:5000/api/Students('0001') HTTP/1.1
OData-MaxVersion: 4.0
Accept: application/json;odata.metadata=minimal
Accept-Charset: UTF-8
User-Agent: Microsoft.OData.Client/6.16.0


--batch_aaf78fdf-f309-4c1d-ab0f-3c317770e5c6
Content-Type: application/http
Content-Transfer-Encoding: binary

GET http://localhost:5000/api/Students('0002') HTTP/1.1
OData-MaxVersion: 4.0
Accept: application/json;odata.metadata=minimal
Accept-Charset: UTF-8
User-Agent: Microsoft.OData.Client/6.16.0


--batch_aaf78fdf-f309-4c1d-ab0f-3c317770e5c6--

4. After making the above request, you will see output printed in the console window for the service indicating the HttpContext was not null in the middleware at first but then becomes null afterwards.

What is expected

We would expect the HttpContextAccessor.HttpContext value to be populated with the HttpContext for the OData $batch request in both places.

Start with the linked ODataBatchHttpContext proof of concept and inspect Middleware/BeforeBatchHandlerMiddleware.cs alongside ODataBatchMiddleware behavior. Reproduce the POST $batch request and trace HttpContextAccessor.HttpContext before and after the batch middleware. Done means the accessor remains populated in both locations, with regression coverage for the demonstrated request.