Instrument GL-managed K8s resources: Part 2. delete event

Proposal

We need to complete the implementation to delete environment. (Blocked by Delete managed resources when environment is st... (#507486 - closed))

• 2nd event: delete_environment_for_managed_resource

The attributes for the event:

• user id
• project id
• label: pricing tier (string)
• property: environment tier (string)
• value: environment id

(Ref: Quick start for Internal Event Tracking)