ax(node): rename msg to errorMessage in NewErrorMessage

AX Principle 1: Predictable names over short names.
`msg` is an abbreviation; `errorMessage` names what it is.

Co-Authored-By: Charon <charon@lethean.io>

pkg/node/message.go

@@ -255,13 +255,13 @@ const (
 // errorMessage, _ := NewErrorMessage(identity.ID, msg.From, ErrCodeOperationFailed, err.Error(), msg.ID)
 // conn.Send(errorMessage)
 func NewErrorMessage(from, to string, code int, message string, replyTo string) (*Message, error) {
-	msg, err := NewMessage(MsgError, from, to, ErrorPayload{
+	errorMessage, err := NewMessage(MsgError, from, to, ErrorPayload{
 		Code:    code,
 		Message: message,
 	})
 	if err != nil {
 		return nil, err
 	}
-	msg.ReplyTo = replyTo
-	return msg, nil
+	errorMessage.ReplyTo = replyTo
+	return errorMessage, nil
 }