CLS2-1299 Show edit history on EYB leads

[stuart-mindt]

Description of change

Ability to list EYB lead change logs and link from the details page. Exposing new /audit endpoint following pattern of other edit history / audit areas of the service.

Checklist

• Has this branch been rebased on top of the current main branch?

  Explanation

  The branch should not be stale or have conflicts at the time reviews are requested.

• Is the CircleCI build passing?

General points

Other things to check

• Make sure fixtures/test_data.yaml is maintained when updating models
• Consider the admin site when making changes to models
• Use select-/prefetch-related field lists in views and search apps, and update them when fields are added
• Make sure the README is updated e.g. when adding new environment variables

See docs/CONTRIBUTING.md for more guidelines.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.63%. Comparing base (126fc2f) to head (1d3f057).
Report is 9 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5980   +/-   ##
=======================================
  Coverage   96.63%   96.63%           
=======================================
  Files        1084     1084           
  Lines       25414    25420    +6     
  Branches     1678     1678           
=======================================
+ Hits        24559    24565    +6     
  Misses        698      698           
  Partials      157      157           

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