### What
Adds `createdByUserId` to all events exposed by unleash. In addition
this PR updates all tests and usages of the methods in this codebase to
include the required number.
###What
Adds an optional sensitive parameter for customHeaders to all current
addons. It is sensitive because the user might be including api key headers.
* fix: slack back link url to point to the feature page
* update snapshots
* update feature link in case project info is available in event
* update missing snapshot
* feat: add new more specific feature/environment events to addons
* Updated strategy change text
* Update all three addon messages for strategy
* Link to new features view for strategy change text
Co-authored-by: Ivar Conradi Østhus <ivarconr@gmail.com>
