message: display for Account number
diff: @@ -99,6 +99,11 @@ impl Account {
  Change::new(*self, 0)
  }
  }
  +impl fmt::Display for Account {
  + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
  + write!(f, "{}", self.0)
  + }
  +}
  impl serde::Serialize for Account
  {
  #[inline]
  