[Sentinel Incidents] 401 Unauthorized error + missing Directory's path

[Powlinett]

Proposed changes

• get a fresh token on every run instead of on every launch
• handle stix2 errors to avoid blocking imports
• check if directory's path is valid before creating a Directory observable

Related issues

• [Sentinel-incident] Authentication problem - Error 401 after several iterations #3325
• [sentinel-incidents]: No values for required properties for Directory bug  #3344

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

Further comments

These are naive solutions to fix the issue as quickly as possible. But better solutions exist, such as:

• add a refresh strategy when the current token is about to expire
• perform data validation (pydantic models) for both Sentinel’s responses and OpenCTI’s objects