Merge branch 'kc-external-url-underscore' into 'master'

Use RFC3986_PARSER when creating a new URI

See merge request gitlab-org/gitlab!59847

lib/api/helpers/related_resources_helpers.rb

@@ -23,10 +23,10 @@ module API
 
         # Using a blank component at the beginning of the join we ensure
         # that the resulted path will start with '/'. If the resulted path
-        # does not start with '/', URI::Generic#build will fail
+        # does not start with '/', URI::Generic#new will fail
         path_with_script_name = File.join('', [script_name, path].select(&:present?))
 
-        URI::Generic.build(scheme: protocol, host: host, port: port, path: path_with_script_name).to_s
+        URI::Generic.new(protocol, nil, host, port, nil, path_with_script_name, nil, nil, nil, URI::RFC3986_PARSER, true).to_s
       end
 
       private

spec/lib/api/helpers/related_resources_helpers_spec.rb

@@ -63,6 +63,12 @@ RSpec.describe API::Helpers::RelatedResourcesHelpers do
       is_expected.to start_with('https://')
     end
 
+    it 'accepts the host if it contains an underscore' do
+      stub_default_url_options(host: 'w_ww.example.com')
+
+      is_expected.to start_with('http://w_ww.example.com/')
+    end
+
     it 'accepts port to be nil' do
       stub_default_url_options(port: nil)