Refactor webhook authorization in server.py using hmac

[dimoschi]

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• Bugfix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality not to work as expected).
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• I have read and followed the CONTRIBUTING.md
  doc.
• Lint and unit tests pass locally with my changes.
• I have added the necessary documentation (if appropriate).

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[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (cf5925d) 61.78% compared to head (efbe9df) 61.78%.

❗ Current head efbe9df differs from pull request most recent head e8bbd2a. Consider uploading reports for the commit e8bbd2a to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main       #3   +/-   ##
=======================================
  Coverage   61.78%   61.78%           
=======================================
  Files          56       56           
  Lines        2999     2999           
=======================================
  Hits         1853     1853           
  Misses       1146     1146           

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[makelarisjr]

LGTM