Added method of updating the name id.

src/message.rs

@@ -291,6 +291,10 @@ impl Message {
         )
     }
 
+    fn reset_name_id<NT>(&mut self, name: NT) where NT: Into<NameType> {
+        self.document_id = name.into();
+    }
+
     fn response<A>(&self, action: A) -> Self
     where
         A: Into<MsgAction>,
@@ -414,6 +418,18 @@ mod messages {
             _ => unreachable!("got {:?}: should have received a reply", action2),
         }
     }
+
+    #[test]
+    fn can_reset_document_id() {
+        let mut msg = Message::new(Name::english("something"), Query::new());
+        let id = Uuid::new_v4();
+        msg.reset_name_id(&id);
+        let name_id = msg.get_document_id();
+        match name_id {
+            NameType::ID(data) => assert_eq!(data, &id),
+            _ => unreachable!("got {:?}, should have been an id", name_id),
+        }
+    }
 }
 
 #[derive(Clone, Debug, Eq, Hash)]