Methods such as withOnUpdateFilter should accept super types

[shawkins]

This is just a minor enhancement request. Filters may be valid against just HasMetadata (or some other parent type) and not require the specific subtype.

[shawkins]

For example on an Informer to add an event handler:

SharedIndexInformer<T> addEventHandler(ResourceEventHandler<? super T> handler)

This allows you to have an event handler that is general to HasMetadata (or whatever else may be in your hierarchy) and use it without additional typing for multiple resource classes.