Upstream ticket: https://secure.phabricator.com/T1562
I'm creating this task in the wikimedia space so that it can be included in T105404 (a list of phab features we might want to pay for).
Facts is the long-term path forward to generating reliable burn-up charts from within phabricator itself (as opposed to relying on phragile).
For details on the relationship between Facts and burnup charts, see T100657.