remove the optional parameter "epr-hint" for the renewable reference 
because its use and associated semantics is very confusing and doesn't 
add functionality.
If the resolver can make use of additional information in the original 
EPR, then the renewable reference minter can add that to the RR-EPR's 
Address and/or ReferenceParameters. In other words, there is no point in 
putting the burden on the client to "guess" whether it makes sense to 
communicate the original EPR or not, because the minter can do it much 
better. Furthermore, the burden is still on the client to verify whether 
the reply is a new EPR or not.
.