Explicitly add ostruct gem in case of Ruby 3.5

Author: numbata

Gemfile

@@ -37,6 +37,9 @@ group :development, :test do
   unless ENV['MODEL_PARSER'] == 'grape-swagger-entity'
     gem 'grape-swagger-entity', git: 'https://github.com/ruby-grape/grape-swagger-entity'
   end
+
+  # Conditionally load 'ostruct' only if Ruby >= 3.5.0
+  gem 'ostruct' if Gem::Version.new(RUBY_VERSION) >= Gem::Version.new('3.5.0')
 end
 
 group :test do

lib/grape-swagger/endpoint.rb

@@ -12,7 +12,7 @@ def content_types_for(target_class)
       if content_types.empty?
         formats       = [target_class.format, target_class.default_format].compact.uniq
         formats       = GrapeSwagger::FORMATTER_DEFAULTS.keys if formats.empty?
-        content_types = GrapeSwagger::CONTENT_TYPE_DEFAULTS.select do |content_type, _mime_type|
+        content_types = GrapeSwagger::CONTENT_TYPE_DEFAULTS.select do |content_type, _mime_type| # rubocop:disable Style/HashSlice
           formats.include? content_type
         end.values
       end