Emit webhook notifications for tag delete and create events
Context
The epic &8213 proposes adding user level data for the GitLab Container Registry. This data would be used to help drive prioritization and investment in the Container Registry category.
Proposal
These notifications include the type of event, the target container repository, and the username. So they have all that's needed for Rails to consume and increment the respective user counters.
Later we'll need to add support for download events, but as mentioned in https://gitlab.com/gitlab-org/gitlab/-/issues/364730#note_1058505347, the registry would generate thousands of these events per second. For iteration and safety (avoid drowning the Rails API that receives these notifications), we should start with just the above events and expand to additional events gradually, including download events. The mechanism will be the same on both sides for all of them, so it will be just a matter of emitting and consuming additional types of events.