Support Solidus v4

[waiting-for-dev]

Summary

We need to relese rc.2 after this one.

Checklist

Check out our PR guidelines for more details.

The following are mandatory for all PRs:

• [x] I have written a thorough PR description.
• [x] I have kept my commits small and atomic.
• [x] I have used clear, explanatory commit messages.

The following are not always needed:

• 📖 I have updated the README to account for my changes.
• 📑 I have documented new code with YARD.
• 🛣️ I have opened a PR to update the guides.
• ✅ I have added automated tests to cover my changes.
• 📸 I have attached screenshots to demo visual changes.

[codecov[bot]]

Codecov Report

Merging #306 (ad23390) into main (4ad2db7) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #306   +/-   ##
=======================================
  Coverage   99.64%   99.64%           
=======================================
  Files          31       31           
  Lines         563      563           
=======================================
  Hits          561      561           
  Misses          2        2           

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