drop URL from Message as it is unfilled and superfluous

model/message.go

@@ -4,18 +4,16 @@ package model
 type Message struct {
 	Updated   uint64
 	ID        string
-	URL       string
 	TS        uint64
 	Author    string
 	Plaintext string
 	ThreadID  string
 }
 
-func NewMessage(ID, URL string, TS uint64, Author, Plaintext string, ThreadID string) Message {
+func NewMessage(ID string, TS uint64, Author, Plaintext string, ThreadID string) Message {
 	return Message{
 		Updated:   updated(),
 		ID:        ID,
-		URL:       URL,
 		TS:        TS,
 		Author:    Author,
 		Plaintext: Plaintext,