replace coherence with guardian

lib/eventos_web/guardian.ex

@@ -0,0 +1,40 @@
+defmodule EventosWeb.Guardian do
+  use Guardian, otp_app: :eventos, permissions: %{
+    superuser: [:moderate, :super],
+    user: [:base]
+  }
+
+  alias Eventos.Accounts
+  alias Eventos.Accounts.User
+
+  def subject_for_token(user = %User{}, _claims) do
+    {:ok, "User:" <> to_string(user.id)}
+  end
+
+  def subject_for_token(_, _) do
+    {:error, :unknown_resource}
+  end
+
+  def resource_from_claims(%{"sub" => "User:" <> uid_str}) do
+    try do
+      case Integer.parse(uid_str) do
+        {uid, ""} ->
+          {:ok, Accounts.get_user!(uid)}
+        _ ->
+          {:error, :invalid_id}
+      end
+    rescue
+      Ecto.NoResultsError -> {:error, :no_result}
+    end
+  end
+
+  def resource_from_claims(_claims) do
+    {:error, :reason_for_error}
+  end
+
+#  def build_claims(claims, _resource, opts) do
+#    claims = claims
+#             |> encode_permissions_into_claims!(Keyword.get(opts, :permissions))
+#    {:ok, claims}
+#  end
+end