Added cent-os to CI tests

[martinkilbinger]

Summary

Continuous integration is now also testing CENT-OS, useful since candide runs on that OS.

Solves #633

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[martinkilbinger]

Not sure it is working. The CI test gets stuck at Waiting for a runner to pick up this job...

[sfarrens]

@martinkilbinger this might mean that they don't have many servers available with that OS. I don't even see centos-latest listed as one of the available runners. Did you check that this image exists somewhere?

[martinkilbinger]

I could not find it either anywhere. So maybe we cannot run this test.

[sfarrens]

In principle, we could set up a Self-Hosted Runner on a machine where we can put a CentOS image. Then we could probably make a separate manually triggered CI workflow for running tests with this runner.

This should not be too difficult to set up, but I don't think it is the most urgent issue to resolve.

[martinkilbinger]

We can leave this issue open; I removed it from the release milestone.