Drop usage of concat when returning link to users message field

test/webpaste-test.el

@@ -54,7 +54,7 @@
   ;; Test to return a link and check that the message logged is the expected one
   (should (equal
            (webpaste-return-url "https://example.com/")
-           "Added https://example.com/ to kill ring."))
+           "Added \"https://example.com/\" to kill ring."))
 
   ;; Check so the kill ring contain the correct contents
   (should (equal (car kill-ring) "https://example.com/")))

webpaste.el

@@ -203,7 +203,7 @@ return it to the user."
   (kill-new returned-url)
 
   ;; Notify user
-  (message (concat "Added " returned-url " to kill ring.")))
+  (message "Added %S to kill ring." returned-url))