Implement UI display and burndown chart calculation for GitHub draft mode
Created by: eseliger
Next PR in the series towards https://github.com/sourcegraph/sourcegraph/issues/7998.
Today at "Let's add support for draft PRs"::
- Extends the
ExternalChangesetState
byDRAFT
(plus UI representation) - Adds drafts to the calculation of historic changeset data
- Exposes the number of drafts on the
changesets.stats
and on thechangesetCountsOverTime
fields
Still to be figured out:
Do webhooks need a special treatment or will they just work? (Maybe there will be pointers in the reviews..