Support for Ruby 3.4.0-preview1

[m-nakamura145]

This Pull Request adds support for Ruby 3.4.0-preview1. Running the current code with Ruby 3.4.0-preview1 results in the following error:

An error occurred while loading ./spec/lib/validators/array_validator_spec.rb. - Did you mean?
                    rspec ./spec/lib/apipie/validator_spec.rb

Failure/Error: require "action_controller/railtie"

LoadError:
  cannot load such file -- bigdecimal
# ./spec/dummy/config/application.rb:3:in '<top (required)>'
# ./spec/dummy/config/environment.rb:5:in '<top (required)>'
# ./spec/spec_helper.rb:10:in '<top (required)>'
# ./spec/lib/validators/array_validator_spec.rb:1:in '<top (required)>'

The reason for this error is that in Rails 7.0.X, bigdecimal is not added to the Gemfile (ref: Rails PR #49039). Therefore, for Ruby 3.4 and above, we need to use Rails 7.1.X for testing.

[mathieujobin]

The reason for this error is that in Rails 7.0.X, bigdecimal is not added to the Gemfile (ref: rails/rails#49039). Therefore, for Ruby 3.4 and above, we need to use Rails 7.1.X for testing.

I think we should also add bigdecimal at least in development dependencies of this gem