drop Python 3.7 support and enforce Python 3.8+ codding standards

[avaldebe]

• drop Python 3.7 support
• enforce code standards for Python 3.8+ using ruff

[avaldebe]

@JohnPaton I would like cut a new release (by creating a tag).

In this PR, I used ruff to update the coding standards to Python 3.8.
In principle ruff can be used as a replacement to black and isort.
Would you want to use ruff for linting and formatting?
or we keep relying on black and isort for formatting?
I could also remove ruff from pre-commit if you find it too much.

Also, is there anything else you would like to include on the new release?

[JohnPaton]

Thanks again!