Update handle_value to only convert values when the value has implemented the Enumerable protocol (#104)

Earlier, I opened https://github.com/sobolevn/recase/pull/97/files because passing a DateTime value to the converter would fail, since it passed the is_map check, but would not work when passed to Enum; I fixed it by hardcoding a new pattern-matched function against DateTimes, and early returning the datetime. However, I now need the same functionality, but for Decimal, which does not exist (and doesn't need to) in this lib. Unfortunately, is_map(%Decimal{}) also returns true, and then fails when passed to Enum.

I think the best solution is to check if the Enumerable protocol is implemented, which may determine if the value can be passed to the next check.

Author: teedang19

lib/recase/utils/enumerable.ex

@@ -41,15 +41,16 @@ defmodule Recase.Enumerable do
     |> Enum.map(fn value -> handle_value(value, fun, &convert_keys/2) end)
   end
 
-  defp handle_value(%DateTime{} = value, _fun, _converter), do: value
-
-  defp handle_value(value, fun, converter)
-       when is_map(value) or is_list(value) do
-    converter.(value, fun)
+  defp handle_value(value, fun, converter) do
+    case Enumerable.impl_for(value) do
+      nil ->
+        value
+
+      _ ->
+        converter.(value, fun)
+    end
   end
 
-  defp handle_value(value, _, _), do: value
-
   defp cast_string(value) when is_binary(value), do: value
 
   defp cast_string(value) when is_atom(value), do: Atom.to_string(value)