Entity slicing: Support loading of particular elements in sets

[oflatt]

Category

Cedar language or syntax features/changes

Describe the feature you'd like to request

#1171 supports loading only some ancestors of entities. However, cedar sets may be just as large as the entity hierarchy. We should extend the entity manifest to have another field which loads particular elements of sets.

I may run out of time to implement this feature before my internship is over, so writing here for posterity.

Describe alternatives you've considered

None

Additional context

No response

Is this something that you'd be interested in working on?

• 👋 I may be able to implement this feature request
• ⚠️ This feature might incur a breaking change