Updated MRR events (#385)
Updated MRR events (#385)

refs https://github.com/TryGhost/Team/issues/1454

Updates the MRR events to store the type column for existing events, this
includes expired events.

---

refs https://github.com/TryGhost/Team/issues/1302

Creates MRR events when the cancelled status of a subscription has changes

---

refs https://github.com/TryGhost/Team/issues/1453

Updates the cancelled MRR Event logic to make a negative MRR delta, this
is behind a flag so everything can be release at once

Co-authored-by: Simon Backx <088e16a1019277b15d58faf0541e11910eb756f6@ghost.org>
TryGhost/Ghost,TryGhost/Ghost,TryGhost/Ghost