Add AsciiDoc snippet for CI/CD Badges

This commit adds CI/CD Badges Snippets for AsciiDoc as requested in #26087.
I've however run into an issue in highlighting the snippet, it seems as if AsciiDoc is currently not being highlighted properly (displayed as plaintext)

Add testcase for to_asciidoc

Update test case for Badges list

app/views/projects/pipelines_settings/_badge.html.haml

@@ -25,3 +25,10 @@
               HTML
             .col-md-10.code.js-syntax-highlight
               = highlight('.html', badge.to_html)
+          .row
+            %hr
+          .row
+            .col-md-2.text-center
+              AsciiDoc
+            .col-md-10.code.js-syntax-highlight
+              = highlight('.adoc', badge.to_asciidoc)

changelogs/unreleased/26087-asciidoc-cicd-badges-snippet.yml

+---
+title: Added AsciiDoc Snippet to CI/CD Badges
+merge_request: 9164
+author: Jan Christophersen

lib/gitlab/badge/metadata.rb

@@ -20,6 +20,10 @@ module Gitlab
         "[![#{title}](#{image_url})](#{link_url})"
       end
 
+      def to_asciidoc
+        "image:#{image_url}[link=\"#{link_url}\",title=\"#{title}\"]"
+      end
+
       def title
         raise NotImplementedError
       end

spec/features/projects/badges/list_spec.rb

@@ -14,7 +14,8 @@ feature 'list of badges' do
       expect(page).to have_content 'build status'
       expect(page).to have_content 'Markdown'
       expect(page).to have_content 'HTML'
-      expect(page).to have_css('.highlight', count: 2)
+      expect(page).to have_content 'AsciiDoc'
+      expect(page).to have_css('.highlight', count: 3)
       expect(page).to have_xpath("//img[@alt='build status']")
 
       page.within('.highlight', match: :first) do
@@ -28,7 +29,8 @@ feature 'list of badges' do
       expect(page).to have_content 'coverage report'
       expect(page).to have_content 'Markdown'
       expect(page).to have_content 'HTML'
-      expect(page).to have_css('.highlight', count: 2)
+      expect(page).to have_content 'AsciiDoc'
+      expect(page).to have_css('.highlight', count: 3)
       expect(page).to have_xpath("//img[@alt='coverage report']")
 
       page.within('.highlight', match: :first) do

spec/lib/gitlab/badge/shared/metadata.rb

@@ -18,4 +18,14 @@ shared_examples 'badge metadata' do
     it { is_expected.to include metadata.image_url }
     it { is_expected.to include metadata.link_url }
   end
+
+  describe '#to_asciidoc' do
+    subject { metadata.to_asciidoc }
+
+    it { is_expected.to include metadata.image_url }
+    it { is_expected.to include metadata.link_url }
+    it { is_expected.to include 'image:' }
+    it { is_expected.to include 'link=' }
+    it { is_expected.to include 'title=' }
+  end
 end