Make PyCIEMSS testable

[fivegrant]

At a high level this PR

1. Reduces the amount code in the API and the worker and moves most into the model itself
2. Tests the conversions of models into keyword arguments for the PyCIEMSS library
3. Formats the code using Black and Ruff
4. Defines GitHub Actions for formatting and testing

To see how to take advantage of these new features, checkout the Testing section in the README.

The PyCIEMSS Service is only a light wrapper that enables REST interaction with the PyCIEMSS library. Moving most of the logic out of the worker and into the model isolates the components that are subject to change when either the contract or the underlying PyCIEMSS library change.

[brandomr]

i'd rename operators.py to tests.py for clarity and also please add a README to the tests directory or somewhere else you'd like that explains the tests, how to run them and how to add one.

[fivegrant]

@brandomr I made your suggested change for now. I'm anticipating that more tests outside of the operation models may arise in the future and it may make sense to have two separate files. There's really no reason to future proof for this though so I'm happy making the change

[fivegrant]

Outstanding TODOs:

• Fix CI
• Test function signature against PyCIEMSS