Replace Jira private images with link

In the Jira Issue Detail page we are not able to show the Jira private
images, we have to replace them with the link to the image.

ee/app/serializers/integrations/jira/issue_detail_entity.rb

@@ -4,7 +4,8 @@ module Integrations
   module Jira
     class IssueDetailEntity < ::Integrations::Jira::IssueEntity
       expose :description_html do |jira_issue|
-        Banzai::Pipeline::GfmPipeline.call(jira_issue.renderedFields['description'], project: nil)[:output].to_html
+        Banzai::Pipeline::JiraGfmPipeline
+          .call(jira_issue.renderedFields['description'], project: project)[:output].to_html
       end
 
       expose :state do |jira_issue|

ee/lib/banzai/filter/jira_private_image_link_filter.rb

+# frozen_string_literal: true
+
+module Banzai
+  module Filter
+    # HTML filter that replaces the Jira private images with the link to the image.
+    class JiraPrivateImageLinkFilter < HTML::Pipeline::Filter
+      PRIVATE_IMAGE_PATH = '/secure/attachment/'
+
+      def call
+        doc.xpath('descendant-or-self::img').each do |img|
+          next unless img['src'].start_with?(PRIVATE_IMAGE_PATH)
+
+          img_link = "#{project.jira_service.url}#{img['src']}"
+          link = "<a href=\"#{img_link}\">#{img_link}</a>"
+
+          img.replace(link)
+        end
+
+        doc
+      end
+
+      def project
+        context[:project]
+      end
+    end
+  end
+end

ee/lib/banzai/pipeline/jira_gfm_pipeline.rb

+# frozen_string_literal: true
+
+module Banzai
+  module Pipeline
+    class JiraGfmPipeline < ::Banzai::Pipeline::GfmPipeline
+      def self.filters
+        [
+          Banzai::Filter::JiraPrivateImageLinkFilter,
+          *super
+        ]
+      end
+    end
+  end
+end

ee/spec/lib/banzai/filter/jira_private_image_link_filter_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Banzai::Filter::JiraPrivateImageLinkFilter do
+  include FilterSpecHelper
+
+  let_it_be(:project) { create(:project) }
+  let_it_be(:jira_service) { create(:jira_service, project: project) }
+  let_it_be(:context) { { project: project } }
+
+  context 'with a Jira private image' do
+    let(:img_link) { '/secure/attachment/10017/10017_jira-logo.jpg' }
+
+    it 'replaces the Jira private images with the link to the image' do
+      doc = filter("<img src=\"#{img_link}\">", context)
+
+      expect(doc.to_html).to eq("<a href=\"#{jira_service.url}#{img_link}\">#{jira_service.url}#{img_link}</a>")
+    end
+  end
+
+  context 'with other image' do
+    let(:img_link) { 'http://example.com/image.jpg' }
+
+    it 'keeps the original image' do
+      doc = filter("<img src=\"#{img_link}\">", context)
+
+      expect(doc.to_html).to eq("<img src=\"#{img_link}\">")
+    end
+  end
+end