Support External Resource State Management for Dependent Resources

[csviri]

When external resources that requires state, it is stored into a ConfigMap, Secret or a dedicated CustomResource. Would be nice to support this patter in Dependent Resources.

[csviri]

Regarding design:

• It would be the good if the event sources would transparently provide such translation, if the resource is created it's ID is stored to an (let's say) ConfigMap, the event source would be aware of such config maps. So if the resource is polled (from a polling event source), it will do the the translation for a resource to the target ID. (For the polling event sources, actually the resource fetcher).

  • it is however assumption is that since the event source reads the mapping of a config map, then this config map is already in the cache, even on startup when operator starts. So this implies that the event source for config map is synchronized first, thus some ordering of event source start might be necessary.

• In terms of dependent resource, the dependent resource will store the ID (on create the ConfigMap) and on cleanup (delete the config map).