What is the primary reason to apply an entity filter to an action in Vlocity Rule Builder?

A guided process allows you to create new product bundles in the Cart.

Context rules frameworks uses a single interface for all of its operations.

When creating a context rule, where can a developer set the rule fail level?

Felix is the Vlocity CPQ Administrator, and he's creating a new product bundle that includes a child product. There can only be one child product at a time in the bundle; it must be added automatically to the cart along with the parent product; and users should be prevented from deleting it. What is the easiest way for Felix to do this?
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