Add mutation testing to pipeline

[basdijkstra]

To get a better insight into the quality of the tests that I use to verify RestAssured .Net builds, I would like to add mutation testing to the pipeline definition. Initially just as a means of getting more information about the quality of the tests, at some point maybe also to fail build if the mutation testing score is too low.

Stryker.Net looks like the obvious choice for a tool.

[basdijkstra]

I'm not going to add mutation tests to the overall pipeline, at least not yet, but I might create a separate one at some point. For now, I added Stryker as a tool to the project in https://github.com/basdijkstra/rest-assured-net/commit/1bf164f29d548d1022b6263f297dbb6a982d36be

I have an initial mutation testing report, and over the next few days and weeks I'll start combing through that to see where I can (should) improve the tests.

[basdijkstra]

Some initial thoughts and results here, I’ll keep working on improving the code and the mutation test results in the weeks / months to come.