Add tests to make sure the container service is actually running

[paddyroddy]

Short Description

Prior to #67, the container service wasn't actually working, but we had no idea. We could alleviate this with some kind of testing to check for a ping from the docker service, and even upload a sample image. An example of which can be seen here https://github.com/UCL-MIRSG/UCLH-MPBE-SRR-XNAT/blob/15d77eb2d203e898685f11b2cf6bf1cabed9fa46/.github/workflows/playbooks.yml#L74-L100

Acceptance Criteria

No response

Dependencies

No response

Details

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[p-j-smith]

Yeah this would be a good first step. Ideally we'd have integration tests to create an XNAT project, upload some DICOM image, and run a container on them (this would also check the path translation between the web and container service is set up correctly)