Adds request_body_multipart method which enables schema properties to be written for multipart upload body

Will inspect the provided hash and add the property file_name to the parameters collection so upload and 3.0 output will work properly

rswag-specs/rswag-specs.gemspec

@@ -18,5 +18,6 @@ Gem::Specification.new do |s|
   s.add_dependency 'activesupport', '>= 3.1', '< 6.0'
   s.add_dependency 'json-schema', '~> 2.2'
   s.add_dependency 'railties', '>= 3.1', '< 6.0'
+  s.add_dependency 'hashie'
   s.add_development_dependency 'guard-rspec'
 end