Refactor API::Instance and reorganize DSL modules

[ericproulx]

Summary

This PR refactors the Grape::API::Instance class and reorganizes methods across DSL modules to improve code organization and maintainability. The changes move routing-related methods from Instance to the DSL::Routing module, simplify instance variable access patterns, and improve test coverage by using actual HTTP calls instead of inspecting internal state.

Changes

API::Instance Refactoring

• Removed attr_readers: Replaced instance and base attr_readers with direct @instance and @base instance variable access
• Simplified compilation: Removed separate compile and call! methods, consolidating logic into compile! and call
• Method visibility: Moved change! from protected to public section for better API consistency
• Updated delegators: Changed def_delegators :base to def_delegators :@base to work with instance variables

DSL Module Reorganization

• Moved methods to DSL::Routing: Relocated given, mounted, and cascade methods from API::Instance to DSL::Routing module where they logically belong
• Method ordering in DSL::Validations: Moved params and contract methods to the top of the module, with reset_validations! moved to private section
• Private method organization: Moved reset_routes! and reset_endpoints! to private section in DSL::Routing
• Instance variable access: Updated evaluate_as_instance_with_configuration to use @base instead of base

API Class Updates

• NON_OVERRIDABLE list: Expanded to include additional methods that should not be overridden (base=, base_instance?, change!, inherit_settings, recognize_path, reset!, top_level_setting=, top_level_setting)
• Delegators: Added change!, recognize_path, and routes to the list of methods delegated to base_instance

Settings Module

• Removed attr_writer: Removed top_level_setting from attr_writer in DSL::Settings (now handled differently)

Test Improvements

• Removed internal state tests: Removed .compile test that checked internal instance state
• Updated .change! test: Now verifies that compilation happens twice after calling change!
• Integration-style routing tests: Updated routing tests to use actual HTTP calls (Rack::MockRequest) instead of checking internal settings hash
• Integration-style validation tests: Updated validation tests to use actual HTTP calls and verify JSON responses instead of directly checking declared_params internal state

Benefits

1. Better code organization: Methods are now located in their appropriate DSL modules
2. Improved test coverage: Tests now verify actual behavior through HTTP calls rather than internal state
3. Cleaner API: Direct instance variable access reduces unnecessary method indirection
4. Better encapsulation: Private methods are properly scoped

Files Changed

• lib/grape/api.rb
• lib/grape/api/instance.rb
• lib/grape/dsl/routing.rb
• lib/grape/dsl/settings.rb
• lib/grape/dsl/validations.rb
• spec/grape/api_spec.rb
• spec/grape/dsl/routing_spec.rb
• spec/grape/dsl/validations_spec.rb
• spec/grape/validations_spec.rb