Include 'published' date of posts in Phame Atom feeds master
Summary: Metadata of Phame blog posts includes the 'updated' date of a blog post. Make them also include the original 'published' date. Patch written by @20after4 from: https://phabricator.wikimedia.org/rPHAB3de500bfc845759d6da82180df0adfc12f973463 Closes T15686 Test Plan: * Go to the Atom feed of blog 1 at `/phame/blog/feed/1/` and look at this `<feed>`'s source * Apply patch and do the same, see additional `<published>` entry just like the `<updated>` * Edit the last blog post in blog 1, then check Atom feed and verify that the published and updated date stamp differ as expected Reviewers: O1 Blessed Committers, valerio.bozzolan Reviewed By: O1 Blessed Committers, valerio.bozzolan Subscribers: tobiaswiese, valerio.bozzolan, Matthew, 20after4, Cigaryno Maniphest Tasks: T15686 Differential Revision: https://we.phorge.it/D25490