Refactor dets repo, dockerfile, and url type; add logger level func

lib/router.ex

@@ -46,7 +46,7 @@ defmodule Shortnr.Router do
   end
 
   def handle_errors(conn, %{kind: _kind, reason: reason, stack: stack}) do
-    Logger.error(inspect(reason), stack: inspect(stack))
+    Logger.error(reason, stack: stack)
 
     {:error, {:internal_server_error, "internal server error"}, conn}
     |> Text.encode_response()

lib/url/repo/dets.ex

@@ -3,7 +3,10 @@ defmodule Shortnr.URL.Repo.DETS do
 
   @impl true
   def get(key) do
-    {:ok, :dets.lookup(:urls, key) |> List.first() |> elem(1)}
+    case :dets.lookup(:urls, key) |> List.first() do
+      {_, url} -> {:ok, url}
+      nil -> {:ok, nil}
+    end
   end
 
   @impl true

lib/url/url.ex

@@ -8,7 +8,12 @@ defmodule Shortnr.URL do
             updated_at: DateTime.utc_now(),
             url: %URI{}
 
-  @type t :: %__MODULE__{id: String.t(), url: URI.t()}
+  @type t :: %__MODULE__{
+          id: String.t(),
+          url: URI.t(),
+          created_at: DateTime.t(),
+          updated_at: DateTime.t()
+        }
 
   @spec create(String.t(), module()) :: {:ok, String.t()} | Transport.error()
   def create(url, repo) do