message: add debugging methods on input::set
diff: @@ -195,10 +195,14 @@ where
  Q::Value: Default,
  {
  fn set(&self, db: &DB, key: &Q::Key, value: Q::Value) {
  + log::debug!("{:?}({:?}) = {:?}", Q::default(), key, value);
  +
  self.set_common(db, key, value, IsConstant(false))
  }
  fn set_constant(&self, db: &DB, key: &Q::Key, value: Q::Value) {
  + log::debug!("{:?}({:?}) = {:?}", Q::default(), key, value);
  +
  self.set_common(db, key, value, IsConstant(true))
  }
  }
  