Use Turbo Stream to flush page cache

[tvdeyen]

What is this pull request for?

Uses a Turbo submit button and a turbo-stream response for the "Flush page cache" button.

Notable changes

Adds one more action to the <alchemy-action> custom element.

Checklist

• I have followed Pull Request guidelines
• I have added a detailed description into each commit message
• I have added tests to cover this change

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.13%. Comparing base (979b5ed) to head (971e361).
⚠️ Report is 9 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3407   +/-   ##
=======================================
  Coverage   97.13%   97.13%           
=======================================
  Files         279      279           
  Lines        7357     7357           
=======================================
  Hits         7146     7146           
  Misses        211      211           

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[mamhoff]

Works! Nice!