Configuration: use YAML.safe_load and allowing aliases (for Ruby 3.1)

[jlestavel]

Brief Summary of Changes

The goal of this PR is to have YAML aliases supported for the config file in Ruby 3.1

By default, Ruby 3.1 will use safe_load so we have to explicitly allow aliases

cf

Psych 4.0 changes Psych.load as safe_load by the default. You may need to use Psych 3.3.2 for migrating to this behavior. [Bug #17866]

in https://www.ruby-lang.org/en/news/2021/12/25/ruby-3-1-0-released/

For example in our project, the config/cloudinary.yml file looks like

---
default: &default
  api_key: '<%= ENV['CLOUDINARY_API_KEY'] %>'
  api_secret: '<%= ENV['CLOUDINARY_API_SECRET'] %>'
staging: &staging
  <<: *default
  cloud_name: our_test_cloud
development: *staging
test: *staging
production:
  <<: *default
  cloud_name: our_prod_cloud

and it's not supported by the current version of the gem

I submitted a similar for another gem, database_consistency, that was accepted if you want to have a look: https://github.com/djezzzl/database_consistency/pull/113

What does this PR address?

• [ ] GitHub issue (Add reference - #XX)
• [ ] Refactoring
• [ ] New feature
• [x] Bug fix
• [ ] Adds more tests

Are tests included?

• [x] Yes
• [ ] No

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I ran the full test suite before pushing the changes and all the tests pass.

[julianrubisch]

I can confirm that this fixes an issue with Ruby 3.1

I was seeing config errors in my app a la ActionView::Template::Error: Must supply cloud_name in tag or in configuration

It turns out that I was also using YAML aliases as suggested in this PR, and checking it out fixed it for me.

[const-cloudinary]

@jlestavel , thank you for contribution!