Validate subdomains (#46)

* test subdomain validation (fails)

* Get test passing

lib/burnex.ex

@@ -52,7 +52,19 @@ defmodule Burnex do
   """
   @spec is_burner_domain?(binary()) :: boolean()
   def is_burner_domain?(domain) do
-    MapSet.member?(@providers, domain)
+    case MapSet.member?(@providers, domain) do
+      false ->
+        case Regex.run(~r/^[^.]+[.](.*)$/, domain) do
+          [_ | [higher_domain]] ->
+            is_burner_domain?(higher_domain)
+
+          nil ->
+            false
+        end
+
+      true ->
+        true
+    end
   end
 
   @doc """

test/burnex_test.exs

@@ -22,6 +22,11 @@ defmodule BurnexTest do
     assert Burnex.is_burner? "\"this is valid! crazy right ?\"@yopmail.fr"
   end
 
+  test "with subdomains" do
+    assert Burnex.is_burner? "hello@mail2.mailinator.com"
+    assert Burnex.is_burner? "hello@reject2.maildrop.cc"
+  end
+
   test "providers list should never be empty" do
     refute Enum.empty?(Burnex.providers)
   end