Generalized Event Sourcing

[csviri]

The intention behind this issue is to provide support for various functionalities that is now missing from the framework. Like:

• Watching Kubernetes resources
• Watching any non K8S resource
• Polling
• Scheduled Controller Execution
• ...

Doing this is a very general and elegant way, by introducing the concept of event sources.
The idea is: event Sources can propagate events about any kind of resource, but also can propagate any kind of event for the controller like retry event, scheduled events or event for periodically execute controller. Of course users can provide their own custom event sources.

This is the scratch of the design from our first design meeting:

[csviri]

In the coming days, we will start refining and prototyping this.