Fix various STOW-RS issues

[nickamzol]

This pull request addresses several STOW-RS issues that were reported in #55 and #56.

• Improved error handling in the STOW-RS service handler
  • Return status code 413 "Payload too large" if the request body exceeds the configured max-upload-size.
• The association pool no longer leaks semaphore permits when the association is rejected (GH-56).
• Added some integration tests for STOW-RS, testing the happy path and the problematic cases

[feliwir]

Just a suggestion how we test against external systems (from our BitBucket pipelines):

  services:
    orthanc: # DICOMweb server for testing
      memory: 256
      image: jodogne/orthanc-plugins

We usually let Orthanc or other docker services run as part of the pipeline. GH has a similar feature https://docs.github.com/en/actions/tutorials/use-containerized-services/use-docker-service-containers

Running tests locally would be less convenient then however

[nickamzol]

Is there a reason the testcontainers approach wouldn’t work for you?
It should work in most CI environments, as long as Docker is available at test time.

As you can see here, the GitHub Actions runner successfully executed the integration tests.

[feliwir]

It was just an idea to reduce rust code that needs to be maintained, but both variants work of course :)