Notify people upon unassignment

When I un-assign someone from a issue, that person should get a notification. It's a vital part in the participation process. It also reduces the risk that two people work on the same issue..

/cc @JobV

Added feature proposal label

Milestone changed to 8.5

Makes sense. I'm thinking you should be able to get notified of everything, but that many people might not be interested in this.

Could solve it with notification level, but in that case you'd also get loads of other emails.

Milestone changed to 8.2

mentioned in merge request !1769 (closed)

Reassigned to @DouweM

mentioned in merge request !1818 (merged)

Status changed to closed by merge request !1818 (merged)

mentioned in commit c9f03247

mentioned in commit b1abe90a

mentioned in merge request !14785