Registering Endecs is not documented

[Noaaan]

When creating custom Endecs (I.E. StructEndecs) you need to register these using the ReflectiveEndecBuilder

An example from Numismatic Overhaul:

// Endec used for shop offers
public static final Endec<ShopOffer> ENDEC = StructEndecBuilder.of(
    BuiltInEndecs.ITEM_STACK.fieldOf("sell", ShopOffer::getSellStack),
    Endec.LONG.fieldOf("price", ShopOffer::getPrice),
    ShopOffer::new
);

// Register method in the "UpdateShopScreenS2CPacket" class
ReflectiveEndecBuilder.register(ShopOffer.ENDEC, ShopOffer.class);