Add stage validation for site_address_is_company_address field

[oliverjwroberts]

Description of change

This PR adds validation for the site_address_is_company_address field; which is now required at the Verify Win stage.

Important

This supports changes being made to the site address question in the project edit requirements form - see FE PR #7486 here.

It also modifies the validation for the site address fields. These are now only required if site_address_is_company_address is not None.

For projects at the active (and subsequent) stage(s), the API will send the site_address_is_company_address and address_* fields in the project.incomplete_fields list. The frontend then uses this list to highlight incomplete fields to the user.

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 96.67%. Comparing base (0c8bd2e) to head (ad305ea).
Report is 19 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5928   +/-   ##
=======================================
  Coverage   96.67%   96.67%           
=======================================
  Files        1070     1070           
  Lines       25382    25385    +3     
  Branches     1672     1672           
=======================================
+ Hits        24538    24541    +3     
  Misses        689      689           
  Partials      155      155           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.