Update the API Authentication.

lib/link_shortener_web/controllers/api/v1/accounts_controller.ex

@@ -0,0 +1,26 @@
+defmodule LinkShortenerWeb.Api.V1.AccountsController do
+  use LinkShortenerWeb, :controller
+
+  alias LinkShortener.Accounts
+  alias LinkShortener.Accounts.User
+  alias LinkShortenerWeb.Auth.Guardian
+
+  action_fallback LinkShortenerWeb.FallbackController
+
+  def sign_up(conn, %{"user" => user_params}) do
+    with {:ok, %User{} = user} <- Accounts.register_user(user_params),
+	 {:ok, token, _claims} <- Guardian.encode_and_sign(user) do
+      conn
+      |> put_status(:created)
+      |> render(:user, %{user: user, token: token})
+    end
+  end
+
+  def sign_in(conn, %{"email" => email, "password" => password}) do
+    with {:ok, user, token} <- Guardian.authenticate(email, password) do
+      conn
+      |> put_status(:created)
+      |> render(:user, %{user: user, token: token})
+    end
+  end
+end

lib/link_shortener_web/controllers/api/v1/accounts_json.ex

@@ -0,0 +1,11 @@
+defmodule LinkShortenerWeb.Api.V1.AccountsJSON do
+  alias LinkShortener.Links.Link
+
+  def user(%{user: user, token: token}) do
+    %{
+      id: user.id,
+      email: user.email,
+      token: token
+    }
+  end
+end

lib/link_shortener_web/controllers/fallback_controller.ex

@@ -21,4 +21,11 @@ defmodule LinkShortenerWeb.FallbackController do
     |> put_view(html: LinkShortenerWeb.ErrorHTML, json: LinkShortenerWeb.ErrorJSON)
     |> render(:"404")
   end
+
+  def call(conn, {:error, :unauthorized}) do
+    conn
+    |> put_status(:unauthorized)
+    |> put_view(html: LinkShortenerWeb.ErrorHTML, json: LinkShortenerWeb.ErrorJSON)
+    |> render(:"401")
+  end
 end