feat: add max_size for file

lib/atomic/uploader.ex

@@ -9,18 +9,29 @@ defmodule Atomic.Uploader do
       use Waffle.Definition
       use Waffle.Ecto.Definition
 
-      def validate({file, _}) do
+      def validate(file, _) do
         file_extension = file.file_name |> Path.extname() |> String.downcase()
 
         case Enum.member?(extension_whitelist(), file_extension) do
-          true -> :ok
-          false -> {:error, "invalid file extension"}
+          true ->
+            if file.size <= max_size() do
+              :ok
+            else
+              {:error, "file size exceeds maximum allowed size"}
+            end
+
+          false ->
+            {:error, "invalid file extension"}
         end
       end
 
       def extension_whitelist do
         Keyword.get(unquote(opts), :extensions, [])
       end
+
+      def max_size do
+        Keyword.get(unquote(opts), :max_size, 500)
+      end
     end
   end
 end