Work Items list [BE] - Add Subscribe to Calendar/RSS Feed - Project

Allow users to subscribe to work item updates via calendar or RSS feeds.

In the legacy issues list, the frontend:

• For RSS feeds, makes a request to a URL like http://127.0.0.1:3000/flightjs/Flight/-/issues.atom?feed_token=glft-ae9704d42a35acd457619a0df252f92870c080c18466b53a042b64f126183eae-1
• For calendar, makes a request to a URL like http://127.0.0.1:3000/flightjs/Flight/-/issues.ics?due_date=next_month_and_previous_two_weeks&feed_token=glft-16e82da962187048b0e80ad416d38625a6286b5da882841accc9051cb3f34018-1&sort=closest_future_date

Questions:

• Should we update the path to flightjs/Flight/-/work_items.atom and flightjs/Flight/-/work_items.ics? - Yes