feat: Add Ruby 4.0 support and compatibility

- Added Ruby 4.0.0 to CI matrix for full test coverage
- Added cgi gem dependency for Ruby 4.0 compatibility (no longer in stdlib)
- Updated style-check job to use Ruby 4.0
- Added mise.toml configuration for Ruby 4.0.0
- Tested and verified gem works with Ruby 4.0.0 (released 2025-12-25)

Ruby version support:
- Ruby 3.0 through 4.0 fully supported
- Added Ruby head for future compatibility testing
- All tests passing with Ruby 4.0.0

Dependencies added for Ruby 4.0:
- cgi gem (extracted from stdlib in Ruby 4.0)

Author: vipulnsward

.github/workflows/ruby.yml

@@ -21,6 +21,7 @@ jobs:
           - 3.2
           - 3.3
           - 3.4
+          - 4.0
           - head
 
     steps:
@@ -43,7 +44,7 @@ jobs:
     strategy:
       matrix:
         ruby-version:
-          - 3.4
+          - 4.0
     steps:
     - uses: actions/checkout@v3
     - name: Set up Ruby

Gemfile

@@ -6,6 +6,7 @@ source 'https://rubygems.org'
 gem 'base64'
 gem 'bigdecimal'
 gem 'mutex_m'
+gem 'cgi'  # Required for Ruby 4.0+ compatibility
 
 gem 'byebug'
 gem 'rake'

mise.toml

@@ -0,0 +1,2 @@
+[tools]
+ruby = "4.0.0"

uploadcare-ruby.gemspec

@@ -43,7 +43,7 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ['lib']
 
-  spec.required_ruby_version = '>= 3.0'
+  spec.required_ruby_version = '>= 3.0'  # Tested with Ruby 3.0 through 4.0
 
   spec.add_dependency 'addressable', '~> 2.8'
   spec.add_dependency 'faraday', '~> 2.12'