Feature: Add GitHub Actions Workflows

[RoryPTB]

Major Changes

• Added unit tests to test the endpoints of the Flask app and automated them in GitHub Actions.
• Automatically build and publish the Docker image to ghcr.io without including a Dockerfile in the repository.
• Added a 'Super-Linter' workflow, which lints the entire codebase.

Minor Changes

• Adjusted parts of the codebase to pass the linter checks.

To Note

• All linter checks pass apart from that of OpenAPI. These checks can be disabled if desired in the test-code-quality.yml file. I've left them enabled for now, since they concern the security of the API and also address the patternProperties attribute which is apparently unsupported according to OpenAPI 3.0. I'll let Dave look more into this.

Future Plans

• Automatically publish new versions of the main branch to PyPI. I'll let Dave decide when he wants us to implement this.

[maaikelimper]

I have the following comments:

• I disagree with the GitHub action that contains the content of the Dockerfile to update the docker-image in ghcr,: either we have a Dockerfile in this repository and we update from this repo, or (as is currently done) we update the image from the GitHub-repo for wis2box
• We can not approve the PR with failing tests @david-i-berry to check if this can be fixed otherwise or the checks will need to be disabled (we can open a separate GitHub-issue with a task to re-enable them when they are fixed)

[david-i-berry]

I agree with @maaikelimper, we either add a Dockerfile and use this to build the image or don't build an image. Given that it is pip installable and only based on python I think any dockerisation should be external.

[RoryPTB]

Okay, that makes sense to me. I agree that being pip-installable, providing a Dockerfile on top is unnecessary. I intended for the PR to be pretty modular anyway, so I'll remove the GHCR action.