feat(api): Pointers supplier

[kezz]

This PR closes #428 by providing the PointersSupplier class which can be stored statically and resolved whenever Audience#pointers() is called to prevent having a bazillion hash maps lying about that all do the same thing.

When implemented, it would look something like this:

 public class MyPointeredObject extends SomePointeredParent implements Pointered {
  private static final PointersSupplier<MyPointeredObject> POINTERS = PointersSupplier.builder()
    .parent(SomePointeredParent.POINTERS) // Fallback to the parent to get pointers from.
    .resolving(Identity.UUID, MyPointeredObject::getUniqueId)
    .resolving(Identity.DISPLAY_NAME, MyPointeredObject::getDisplayName)
    .build();

  @Override
  public Pointers pointers() {
    return POINTERS.view(this);
  }
}

[zml2008]

Looks good -- probably more useful for native implementations than -platform because -platform is more dynamic about which sources it adds pointers from.

One thing i'd like to see is some sort of 'inheritance' functionality. toBuilder() is close, but has a type parameter of T rather than U extends T, which would prevent it from being used to, for example, have a PointersSupplier for ServerPlayer extend from CommandSource.

[kezz]

One thing i'd like to see is some sort of 'inheritance' functionality. toBuilder() is close, but has a type parameter of T rather than U extends T, which would prevent it from being used to, for example, have a PointersSupplier for ServerPlayer extend from CommandSource.

Do you think it would make more sense for the builder to have a fallback or parent method where you pass in your instance of the parent class or it's pointers supplier object?

[zml2008]

Do you think it would make more sense for the builder to have a fallback or parent method where you pass in your instance of the parent class or it's pointers supplier object?

@kezz I think that would be a reasonable option

[kezz]

Rebased and addressed zml's comments. You can now pass a parent to the supplier builder - see the PR description for an updated example.

changes have been made