Create a pure atom feed from user activity entry feeds, i.e. do not
show specific OStatus/Activity Stream elements. Title, summary,
published, id and author is enough to work with to begin with.

Comply to the Atom standard and create and extensible feed
framework which is ready for the Activity Stream extensions.

Make the feed discoverable from the user profile page.

Incorporate activity stream namespace and represent objects and
verbs in the stream according to the Activity Stream base schema.
If Atom feed and the feed framework, as well as the model structure
were created with extensions in mind, this shouldn't be difficult.