[Spycloud] Create external import connector

[Powlinett]

Proposed changes

⚠️ This PR overrides previous Spycloud PR #3319

• Use/adapt external import template
• Validate config/env variables
• Create Spycloud API client handling authentication, filters, retry strategy...
• Create Spycloud classes (BreachCatalog and BreachRecord)
• Create OpenCTI classes (Author, Incident, observables...)
• Add unit tests
• Add pyproject.toml
• Update Docker build

Related issues

• [SpyCloud] Create the connector #2563

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality using different use cases
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

[flavienSindou]

Nice and clear documented code.
Some small remarks but a really good implementation.

You should add a test-requirements.txt file for the CI to launch your tests

I test the connector locally and I'll approve it.