Use Redis for CacheMarkDownField on non AR models

This allows using `CacheMarkdownField` for models that are not backed
by ActiveRecord.

When the including class inherits `ActiveRecord::Base` we include
`Gitlab::MarkdownCache::ActiveRecord::Extension`. This will cause the
markdown fields to be rendered and the generated HTML stored in a
`<field>_html` attribute on the record. We also store the version
used for generating the markdown.

All other classes that include this model will include the
`Gitlab::MarkdownCache::Redis::Extension`. This add the `<field>_html`
attributes to that model and will generate the html in them. The
generated HTML will be cached in redis under the key
`markdown_cache:<class>:<id>`. The class this included in must
therefore respond to `id`.

1 files changed, 2 insertions, 1 deletions

diff --git a/spec/helpers/markup_helper_spec.rb b/spec/helpers/markup_helper_spec.rb
index c3956ba08fd..597c8f836a9 100644
--- a/spec/helpers/markup_helper_spec.rb
+++ b/spec/helpers/markup_helper_spec.rb
@@ -78,7 +78,8 @@ describe MarkupHelper do
     let(:link)    { '/commits/0a1b2c3d' }
     let(:issues)  { create_list(:issue, 2, project: project) }
 
-    it 'handles references nested in links with all the text' do
+    # Clean the cache to make sure the title is re-rendered from the stubbed one
+    it 'handles references nested in links with all the text', :clean_gitlab_redis_cache do
       allow(commit).to receive(:title).and_return("This should finally fix #{issues[0].to_reference} and #{issues[1].to_reference} for real")
 
       actual = helper.link_to_markdown_field(commit, :title, link)