subscribe and unsubscribe both have an object called Book to clarify I've renamed it to SubscribeBook and UnsubscribeBook
UNLModify has a field unlmodify_disabling which can only be 0 or 1. Instead of being type u8 I've added a enum UNLModifyDisabling making UNLModifyError obsolete.
Added XRPLAmountException to handle amount.try_into()Decimal errors
High Level Overview of Change
This PR simply resolves some
TODOs._serdedocumentationsubscribeandunsubscribeboth have an object calledBookto clarify I've renamed it toSubscribeBookandUnsubscribeBookUNLModifyhas a fieldunlmodify_disablingwhich can only be0or1. Instead of being typeu8I've added a enumUNLModifyDisablingmakingUNLModifyErrorobsolete.XRPLAmountExceptionto handleamount.try_into()Decimalerrors