Send favicons in Fever API

lib/frenzy_web/controllers/fever_controller.ex

@@ -158,9 +158,26 @@ defmodule FrenzyWeb.FeverController do
     end
   end
 
-  defp favicons(res, _user, %{"favicons" => _}) do
+  defp favicons(res, user, %{"favicons" => _}) do
+    favicons =
+      user.groups
+      |> Enum.flat_map(& &1.feeds)
+      |> Enum.map(fn feed ->
+        case feed.favicon do
+          nil ->
+            nil
+
+          favicon ->
+            %{
+              id: feed.id,
+              data: favicon |> String.trim_leading("data:")
+            }
+        end
+      end)
+      |> Enum.reject(&is_nil/1)
+
     res
-    |> Map.put(:favicons, [])
+    |> Map.put(:favicons, favicons)
   end
 
   defp favicons(res, _, _), do: res