chore: upgrade to rails 7.1

[ekowidianto]

Ref:

• https://guides.rubyonrails.org/6_1_release_notes.html
• https://guides.rubyonrails.org/upgrading_ruby_on_rails.html#upgrading-from-rails-6-0-to-rails-6-1
• https://www.fastruby.io/blog/rails/upgrades/upgrade-rails-from-6-0-to-6-1.html
• https://www.shakacode.com/blog/upgrade-rails-6-1-to-7/

Todo List (for this PR):

6.1

• [x] Bumping into Rails 6.1 and all its related gems
• [x] Fix the bug that are detected in both FactoryBot and also RSpec testcases
• Tests some of the pages one by one (optional)

7.0

• [ ] Bumping into Rails 7.0 and all its related gems
• [ ] Fix the bug that are detected in both FactoryBot and also RSpec testcases
• Tests some of the pages one by one (optional)

7.1

• [ ] Bumping into Rails 7.1 and all its related gems
• [ ] Fix the bug that are detected in both FactoryBot and also RSpec testcases
• Tests some of the pages one by one (optional)

(before updating the Ruby version)

• [ ] Tests the pages one by one