Upgrade to Rails 7.2

[Ithanil]

Updated Rails from 7.1 to 7.2 and made relevant changes accordingly.

Steps:

1. Address deprecations (Fix deprecations to enable move to Rails 7.2 #1124) [✅]
2. Upgrade to Rails 7.2 (merge in changes in generated config files, load new defaults, update schema.rb) [✅]

Important notes:

• I have preserved the configuration of SECRET_KEY_BASE as a plaintext env variable, instead of actually utilizing the "new" (since Rails 5 I think) credentials mechanism, despite the removal of the old Rails secrets mechanism in 7.2. Hence, there is no breaking change here. Credits to https://dev.to/yegorov/how-to-continue-to-use-railsapplicationsecrets-in-rails-72-32c7
• I have adapted the new Puma thread count default of 3 (from 5)

Links

Notable deprecations:
rails/rails#48134
rails/rails#47675
https://www.stefanwienert.de/blog/2023/10/24/rails-7-1-migrate-from-secrets-yml-to-credentials-enc-yml-short/
https://dev.to/yegorov/how-to-continue-to-use-railsapplicationsecrets-in-rails-72-32c7

Notable changes with 7.2:
https://guides.rubyonrails.org/7_2_release_notes.html
rails/rails#50450

Testing Steps (more testing welcome!)

• all Rails Tests / RSpecs pass
• basic API calls (create, join, getMeetings, etc.)
• getRecordings / recording playback
• most common rake tasks

Fixed Issues

#1124