Worker Producer Queue for Apps

[schrieveslaach]

When multiple builds of a feature branch of a microservice run in parallel most of the builds would fail because PREvant rejects the deployment requests with 409 Conflict. Instead PREvant could manage a queue of deployment (and deletion) requests and a background task works this off in order by removing a request from the queue and forwarding it to the infrastructure.

New subsequent request for the same app should be consolidated with requests that haven't been removed from the queue yet.

This approach enables PREvant to provide an async API so that HTTP clients to not run into HTTP timeouts anymore.