Support Redmine master

[otegami]

close: https://github.com/clear-code/redmine_full_text_search/issues/126

• Rails uses the ApplicationRecord as a default parent class of all models instead of ActiveRecord::Base
  • ref: https://www.redmine.org/issues/38975
  • ref: https://rubyonrails.org/2016/6/30/Rails-5-0-final
• In Rails 7, the .schema_format= API is moved from ActiveRecord::Base to ActiveRecord
  • ref: https://github.com/rails/rails/pull/42442
• Use the actual path under /plugins using symbolic links
  • Because __dir__ resolves the symbolic link
• In Rails v7.1, ActiveSupport::TestCase.fixture_path will be deprecated
  • ref: https://github.com/rails/rails/pull/47675
  • ref: https://github.com/rails/rails/pull/47764

What I didn't

• Interact with all the provided features
  • I determined there were no errors since the CI passed

[kou]

Could you split this to 4 PRs?

1. Rails uses the ApplicationRecord as a default parent class of all models instead of ActiveRecord::Base
2. In Rails 7, the .schema_format= API is moved from ActiveRecord::Base to ActiveRecord
3. Use the actual path under /plugins using symbolic links
4. In Rails v7.1, ActiveSupport::TestCase.fixture_path will be deprecated

The 2. must be the first PR because it's the cause of current CI failure: https://github.com/clear-code/redmine_full_text_search/actions/runs/8126442854/job/22210192673#step:8:301

NoMethodError: undefined method `schema_format=' for ActiveRecord::Base:Class

[otegami]

Sure. I will close this PR and make 4 PRs.