Add coordinator trade pipeline end-to-end tests

[Reckless-Satoshi]

What does this PR do?

This PR introduces integration tests with end-to-end trades to the coordinator backend.

• Implement API tests class that asserts all client responses against our OpenAPI specs file.
• Implement test class with functionality to create robots, create orders, take them etc. Partial work done only, more tests to be introduced.
• Implement regtest docker-compose testing environment with LND and CLN backend and a user node.
• Create github wofklow for integration tests that uses matrix strategy for different versions of, LND, CLN, Bitcoin Core and Python for the Django backend

This PR also has some bug fixes and improvements to the API specs done while implementing the firsts integration tests.

Checklist before merging

• Install pre-commit and initialize it: pip install pre-commit, then pre-commit install. Pre-commit installs git hooks that automatically check the codebase. If pre-commit fails when you commit your changes, please fix the problems it points out.