Add the helper to make a user log in.

test/support/helpers.ex

@@ -40,4 +40,15 @@ defmodule DecentralisedBookIndex.Helpers do
     |> DateTime.add(seconds)
     |> DateTime.to_iso8601()
   end
+
+  @doc """
+  Logs the given `user` into the `conn`.
+
+  It returns an updated `conn`.
+  """
+  def log_in_user(conn, user) do
+    conn
+    |> Phoenix.ConnTest.init_test_session(%{})
+    |> AshAuthentication.Plug.Helpers.store_in_session(user)
+  end
 end