Merge branch 'ce_issue_10672' into 'master'

[CE] - Load 'Gitlab::Jira::Middleware' if it exists

See merge request gitlab-org/gitlab-ce!26665

config/initializers/jira.rb

+# frozen_string_literal: true
+
+# Changes JIRA DVCS user agent requests in order to be successfully handled
+# by our API.
+#
+# Gitlab::Jira::Middleware is only defined on EE
+#
+# Use safe_constantize because the class may exist but has not been loaded yet
+if "Gitlab::Jira::Middleware".safe_constantize
+  Rails.application.config.middleware.use(Gitlab::Jira::Middleware)
+end