Block reload config files in Railtie if they already uploaded

[Nuzair46]

Continuation for #353
Fixes #352

[Nuzair46]

@pkuczynski @vovanmozg @Fryguy
Please take a look at this PR.
Its continuing the work by @vovanmozg in #353

[Copilot]

Pull Request Overview

This PR blocks the reloading of configuration files in the Rails Railtie if they have already been uploaded, preventing duplicate loading of settings. The change adds a guard clause to check if the configuration constant is already defined before proceeding with the default configuration loading.

Key changes:

• Added guard clause in Railtie to prevent duplicate config loading
• Enhanced test coverage for Rails context configuration scenarios
• Updated documentation to clarify custom settings file loading

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
lib/config/integrations/rails/railtie.rb	Added guard clause to prevent reloading if config constant already exists
spec/config_spec.rb	Added comprehensive test suite for Rails context configuration loading
spec/config_env_spec.rb	Added ENV backup/restore functionality for test isolation
spec/app/rails_*/config/boot.rb	Added logger requirement across Rails test apps
spec/app/rails_5.2/config/application.rb	Commented out config_available? call for test context
README.md	Added documentation for custom settings file loading

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