Pipebird agent should notify control plane on graceful shutdown

[cumason123]

Is your feature request related to a problem? Please describe. Currently we have no way to notify the control plane when an instance is terminated. If you spin up multiple pipebird instances and tear them down, then our control plane has no way to track their state.

Describe the solution you'd like I would like to notify the control plane when the instance receives a SIGTERM such that the control plane can delete the deployment.

Describe alternatives you've considered We could enable users to delete instances on their control plane dashboard. This may lead to desync of deployments being deleted for currently running instances however.