Automatic linting, testing and test-coverage for all pushes

[pacharanero]

On the Flask API repo we had automated tests running when the Action to push to the alpha or unstable server was run.

Now that this code has been refactored out into its own repo, we can make this kind of check run automatically whenever we push to any branch, even a new feature branch.

https://docs.github.com/en/actions/guides/building-and-testing-python

[eatyourpeas]

Currently tests run automatically when a new release is made. We could make it on every push also.

[pacharanero]

This issue still requires actioning. I propose collecting a few similar pieces of outstanding work on the rcpchgrowth-python package and working on them as a small cluster of work projects.

There is a good example of how to set up the testing here, on the nhs-number package workflow
uk-fci/nhs-number@40e710f