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, 2 deletions

diff --git a/spec/requests/api/projects_spec.rb b/spec/requests/api/projects_spec.rb
index 4a0d727faea..861eb12b94c 100644
--- a/spec/requests/api/projects_spec.rb
+++ b/spec/requests/api/projects_spec.rb
@@ -232,7 +232,7 @@ describe API::API, api: true  do
       post api('/projects', user), project
 
       project.each_pair do |k, v|
-        next if %i{ issues_enabled merge_requests_enabled wiki_enabled }.include?(k)
+        next if %i[has_external_issue_tracker issues_enabled merge_requests_enabled wiki_enabled].include?(k)
         expect(json_response[k.to_s]).to eq(v)
       end
 
@@ -360,7 +360,7 @@ describe API::API, api: true  do
       post api("/projects/user/#{user.id}", admin), project
 
       project.each_pair do |k, v|
-        next if k == :path
+        next if %i[has_external_issue_tracker path].include?(k)
         expect(json_response[k.to_s]).to eq(v)
       end
     end