MinecraftForge offers a capability API

• Move the net.minecraftforge.common.util package to another sub-project
• Still need to implement special cases for
  • ChestBlockEntity
  • LockableContainerBlockEntity
  • AbstractFurnaceBlockEntity
  • BrewingStandBlockEntity
  • LivingEntity
  • HorseBaseEntity
  • StorageMinecartEntity
  • PlayerEntity

CapabilityInject on methods require a CapabilityRegisteredCallback to be registered. CapabilityInject for fields requires a bridge callback method to be created, where the field is assigned from.