write first test and let changeset errors return error json in controller

lib/entendu_web/controllers/fallback_controller.ex

@@ -0,0 +1,10 @@
+defmodule EntenduWeb.FallbackController do
+  use EntenduWeb, :controller
+
+  def call(conn, {:error, %Ecto.Changeset{} = changeset}) do
+    conn
+    |> put_status(:unprocessable_entity)
+    |> put_view(EntenduWeb.ChangesetView)
+    |> render("error.json", changeset: changeset)
+  end
+end

lib/entendu_web/controllers/link_controller.ex

@@ -9,27 +9,33 @@ defmodule EntenduWeb.LinkController do
   alias Entendu.Links
   alias Links.Link
   alias Ecto.Changeset
+  alias EntenduWeb.FallbackController
+
+  action_fallback(FallbackController)
 
   def just_page(conn, _params) do
     render(conn, "just.html")
   end
 
-  defparams first_step %{
-    burn_after_reading: [field: :boolean, default: false],
-    expires: :utc_datetime,
-    filename: :string,
-    filetype: :string,
-    text_content: :string,
-    file_content: :string
-  }
+  defparams(
+    first_step(%{
+      burn_after_reading: [field: :boolean, default: false],
+      expires: :utc_datetime,
+      filename: :string,
+      filetype: :string,
+      text_content: :string,
+      file_content: :string
+    })
+  )
 
   def just(conn, params) do
     with %Changeset{valid?: true} = changeset <- first_step(params),
-        link_params <- Params.to_map(changeset),
-        {:ok, %Link{} = link} <- Links.create_link(link_params) do
+         link_params <- Params.to_map(changeset),
+         {:ok, %Link{} = link} <- Links.create_link(link_params) do
       conn
+      |> put_status(:created)
       |> assign(:link, link)
-      |> render("show_authorized", link: link)
+      |> render("show_authorized.json", %{link: link})
     end
   end