[SONIC-808] PayPal Webhooks implementation for refunds

[shafqatfarhan]

Merge checklist:
Check off if complete or not applicable:

• Documentation updated (not only docstrings)
• Fixup commits are squashed away
• Unit tests added/updated
• Manual testing instructions provided
• Noted any: Concerns, dependencies, migration issues, deadlines, tickets

Post-merge:

• Backported to latest and next named releases

[github-actions]

Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
commerce_coordinator
urls.py
commerce_coordinator/apps/commercetools
clients.py					368-369, 509-510
signals.py					62
tasks.py					88-99
utils.py
commerce_coordinator/apps/commercetools/tests
test_utils.py
commerce_coordinator/apps/paypal
signals.py
urls.py
views.py					45, 60-61
commerce_coordinator/apps/paypal/tests
test_views.py
commerce_coordinator/apps/stripe
pipeline.py					238
Project Total

This report was generated by python-coverage-comment-action