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, 2 insertions, 0 deletions

diff --git a/spec/services/git_push_service_spec.rb b/spec/services/git_push_service_spec.rb
index 22991c5bc86..8e3e12114f2 100644
--- a/spec/services/git_push_service_spec.rb
+++ b/spec/services/git_push_service_spec.rb
@@ -448,6 +448,8 @@ describe GitPushService, services: true do
       let(:jira_tracker) { project.create_jira_service if project.jira_service.nil? }
 
       before do
+        # project.create_jira_service doesn't seem to invalidate the cache here
+        project.has_external_issue_tracker = true
         jira_service_settings
 
         WebMock.stub_request(:post, jira_api_transition_url)