Add our fork of wagtaildraftsharing to Bedrock

[stevejalim]

This branch was originally a test harness for using mozmeao/wagtaildraftsharing#1 in bedrock, but now it's just adding in the completed work from that PR.

In order to test drive this branch (using the steps outlined for reviewing that PR liked above), you need to carry out these steps:

1. Check out this branch by running git fetch on whatever your mozilla origin is called, then git switch 15181--wagtail-page-review-without-auth.
2. make install-local-python-deps to get requirements installed - check that our fork of wagtaildraftsharing is being installed
3. ./manage.py migrate
4. Start your runserver as usual and then go to Add Wagtail 6 support + extra way to create a sharing link mozmeao/wagtaildraftsharing#1 to continue testing

Related Issues

Resolves #15181

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.36%. Comparing base (847aeae) to head (d8556dc).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #15232   +/-   ##
=======================================
  Coverage   78.35%   78.36%           
=======================================
  Files         162      162           
  Lines        8316     8318    +2     
=======================================
+ Hits         6516     6518    +2     
  Misses       1800     1800           

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[pmac]

📜

[stevejalim]

@alexgibson FYI draftsharing work is now landing in mozilla/bedrock:main - thanks for the review of the library over on mozmeao/wagtaildraftsharing