Activate ktlint on core and cli modules

changed milestone to %Mailbox

added Sponsor 6 label

mentioned in merge request !6 (merged)

assigned to @grote

added S: in code review label

mentioned in merge request !10 (merged)

mentioned in commit f28b80ce

closed with merge request !10 (merged)

added R: fixed label and removed S: in code review label

added Mailbox label

added Weight: 1 label

added Mailbox app label