fix: Webhook integration not rebuilding environment

[khvn26]

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• I have added information to docs/ if required so people know about the feature!
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• I have filled in the "How did you test this code" section below?
• I have used a Conventional Commit title for this Pull Request

Changes

This fixes a problem when adding, updating or removing a webhook integration does not trigger an environment document rebuild.

How did you test this code?

Added a unit test specifically for the case. I did make sure the test was failing without the added changes.

[vercel]

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3 Skipped Deployments

Name	Status	Preview	Comments	Updated (UTC)
docs	⬜️ Ignored (Inspect)			Sep 18, 2024 5:24pm
flagsmith-frontend-preview	⬜️ Ignored (Inspect)			Sep 18, 2024 5:24pm
flagsmith-frontend-staging	⬜️ Ignored (Inspect)			Sep 18, 2024 5:24pm

[github-actions]

Docker builds report

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-e2e:pr-4641	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-api-test:pr-4641	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-api:pr-4641	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith:pr-4641	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-private-cloud:pr-4641	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-frontend:pr-4641	Finished ✅	Results ✅

[github-actions]

Uffizzi Preview deployment-56416 was deleted.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.17%. Comparing base (b74adbd) to head (4694bdf).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4641   +/-   ##
=======================================
  Coverage   97.17%   97.17%           
=======================================
  Files        1162     1163    +1     
  Lines       40267    40274    +7     
=======================================
+ Hits        39130    39138    +8     
+ Misses       1137     1136    -1     

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