feat: Add configurable session store with ActiveRecord

[Quentinchampenois]

🎩 Description

Please describe your pull request.

When user creates an initiative, and body is heavy, it raises a ActionDispatch::Cookies::CookieOverflow error.

This PR add the possibility to configure ActiveRecord SessionStore using env var RAILS_SESSION_STORE

📌 Related Issues

Link your PR to an issue

• Related to Bug on initiatives due to description length decidim/decidim#9845
• Notion card

Testing

Describe the best way to test or validate your PR.

Example:

• Run rails server with ActiveRecord env var : RAILS_SESSION_STORE=active_record bundle exec rails s
• Create initiative with large body
• See no error

Tasks

• Add reversible migration
• Allow to switch the session store

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (7182e42) 89.37% compared to head (898b07e) 65.93%.

Additional details and impacted files

@@             Coverage Diff              @@
##           develop     #472       +/-   ##
============================================
- Coverage    89.37%   65.93%   -23.44%     
============================================
  Files           64       58        -6     
  Lines         1581     1547       -34     
============================================
- Hits          1413     1020      -393     
- Misses         168      527      +359     

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[luciegrau]

Seems to work great, thank you! 😄