* upgrade helmet to version 4
* deps(short-uuid): upgrade to version 4, closes#12573
* deps(slack): upgrade to version 4
* deps(slack): upgrade to version 5, closes#11442
* deps(amplitude): upgrade to latest version use api v2
* fix tests
* slack tests: return promise
* refactor slack setup for tests
* fix slack unit tests
* remove duplicate module.exports statement
* remove commented-out footer in Slack slur notification
There's no need for anything to replace this footer.
* swap order of flag actions to put most critical first
This causes moderators to be notified before the flagged message's flagCount is incremented, because if something happens to prevent the flagGroupMessage Promise from resolving, we still want to mods to see the notification.
* limit chat message flagging ability for new players
Players who created accounts less than three days ago can flag posts
but that does not contribute to the posts' flagCount. This prevents
a troll from maliciously hiding innocent messages by creating new
accounts to flag them.
* add tests
* fix other tests
