Fix webhook signature verification for Python 3.11+ and add CI test coverage

[cobanfurkanx]

Summary

In Python 3.11+, string formatting on \Enum\ types returns the enum representation (e.g. \WebhookEventType.API_VERIFY_AND_AUTH) instead of the member value (\API_VERIFY_AND_AUTH).

Because \HookAdapter.is_webhook_verified\ relied on string formatting of \webhook_data.event_type\ and \webhook_data.status, the computed HMAC payload differed from the signature on Python 3.11/3.12, causing \is_webhook_verified\ to fail.

Changes

• Extract .value\ from \webhook_data.event_type\ and \webhook_data.status\ via \getattr, supporting both \Enum\ instances and plain strings.
• Add test cases in \ est_hook_sample.py\ for string values and \None\ argument handling.
• Include \ ests.test_hook_sample\ in .github/workflows/craftgate-build.yml\ so webhook verification is verified across the Python 3.7-3.12 test matrix in CI.