Accessing CustomResource Cache from EventSources

[snowdrop-bot]

In event sources there are cases - especially when we want to associate the dependent resource with the main custom resource - when we want to search or have access to information to related custom resource, see:

https://github.com/java-operator-sdk/java-operator-sdk/blob/7eb3aa7f26e72ab59be04d87a8937440935d3945/sample-operators/tomcat-operator/src/main/java/io/javaoperatorsdk/operator/sample/WebappController.java#L45-L47
(In v2 there is better API to access the cache)

Should we support this explicitly like having a way to inject the cache?

Or support an indexing with some additional facilities for eventing?
see: Issues is related to: operator-framework#665
Note that for example the mentioned Tomcat sample we would need just a index the UID when the Tomcat CR appeared.

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operator-framework#666

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$upstream:666$