Update the edit function in Links to support existing links.

lib/link_shortener/links/links.ex

@@ -49,9 +49,9 @@ defmodule LinkShortener.Links do
     |> Repo.all()
   end
 
-  def edit_one(%Link{} = link) do
+  def edit_one(%Link{} = link, attrs \\ %{}) do
     link
-    |> Link.changeset(%{})
+    |> Link.changeset(attrs)
   end
 
   def update_one(%Link{} = link, changes) do