Mutable objects used for immutable values

[snazy]

Describe the bug

PolarisEntityCore type hierarchy is used to represent the persisted (or about to be persisted) state. Especially the already persisted state should be considered immutable. Instances of PolarisEntityCore are also cached via org.apache.polaris.core.persistence.cache.EntityCacheEntry#entity.

PolarisEntityCore + PolarisBaseEntity type hierarchy exposes public setters for effectively all properties. This makes it very easy to (accidentally?) modify entity instances that are cached or in any other way shared. Although the types have some "copy constructors", the risk of modifying attributes is still there. Even if a legit change to a property of a shared object would not be correct, given the Java memory model guarantees.

To Reproduce

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Actual Behavior

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Expected Behavior

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Additional context

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System information

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[sclee01]

Hi @snazy , I'd like to take this on. I agree the current mutability of shared PolarisEntityCore instances is risky. I'll focus on reinforcing immutability and preventing accidental mutation, especially around cached objects.