Add markdown cache columns to the database, but don't use them yet

This commit adds a number of _html columns and, with the exception of Note,
starts updating them whenever the content of their partner fields changes.

Note has a collision with the note_html attr_accessor; that will be fixed later

A background worker for clearing these cache columns is also introduced - use
`rake cache:clear` to set it off. You can clear the database or Redis caches
separately by running `rake cache:clear:db` or `rake cache:clear:redis`,
respectively.

1 files changed, 4 insertions, 1 deletions

diff --git a/spec/services/merge_requests/merge_service_spec.rb b/spec/services/merge_requests/merge_service_spec.rb
index e49a0d5e553..ee53e110aee 100644
--- a/spec/services/merge_requests/merge_service_spec.rb
+++ b/spec/services/merge_requests/merge_service_spec.rb
@@ -60,7 +60,10 @@ describe MergeRequests::MergeService, services: true do
 
         let(:jira_tracker) { project.create_jira_service }
 
-        before { jira_service_settings }
+        before do
+          project.update_attributes!(has_external_issue_tracker: true)
+          jira_service_settings
+        end
 
         it 'closes issues on JIRA issue tracker' do
           jira_issue = ExternalIssue.new('JIRA-123', project)