Map authorization for IssueAuth (#108)

Added a new mehod map_authorization for IssueBundle to support workflow
in Librustzcash where we trasform a Transaction from one authorization
state (e,g, Unauthorized) to another (e.g. Aurhotized/Signed) by
transfroming all underlying bundles

src/issuance.rs

@@ -255,6 +255,19 @@ impl<T: IssueAuth> IssueBundle<T> {
  authorization,
  }
  }
+
+ /// Transitions this bundle from one authorization state to another.
+ pub fn map_authorization<T2: IssueAuth>(
+ self,
+ map_auth: impl FnOnce(T) -> T2,
+ ) -> IssueBundle<T2> {
+ let authorization = self.authorization;
+ IssueBundle {
+ ik: self.ik,
+ actions: self.actions,
+ authorization: map_auth(authorization),
+ }
+ }
 }
 
 impl IssueBundle<Unauthorized> {