create API Key resource

lib/ex_twilio/resources/key.ex

@@ -0,0 +1,23 @@
+defmodule ExTwilio.Key do
+  @moduledoc """
+  Represents an API Key resource in the Twilio API.
+
+  - [Twilio docs](https://www.twilio.com/docs/iam/keys/api-key)
+  """
+  defstruct account_sid: nil,
+            date_created: nil,
+            date_updated: nil,
+            friendly_name: nil,
+            secret: nil,
+            sid: nil
+
+  use ExTwilio.Resource,
+    import: [
+      :find,
+      :create,
+      :update,
+      :destroy
+    ]
+
+  def parents, do: [:account]
+end