add authh header

lib/gringotts/gateways/monei.ex

@@ -429,6 +429,10 @@ defmodule Gringotts.Gateways.Monei do
     ]
   end
 
+  defp auth_headers(opts) do
+    [{:Authorization, opts[:config][:password]} | @default_headers]
+  end
+
   # Makes the request to MONEI's network.
   @spec commit(atom, String.t(), keyword, keyword) :: {:ok | :error, Response.t()}
   defp commit(:post, endpoint, params, opts) do
@@ -442,7 +446,7 @@ defmodule Gringotts.Gateways.Monei do
         url
         |> HTTPoison.post(
           {:form, params ++ validated_params ++ auth_params(opts)},
-          @default_headers
+          auth_headers(opts)
         )
         |> respond
     end

test/gateways/monei_test.exs

@@ -134,10 +134,10 @@ defmodule Gringotts.Gateways.MoneiTest do
     test "that all auth info is picked.", %{bypass: bypass, auth: auth} do
       Bypass.expect_once(bypass, "POST", "/v1/payments", fn conn ->
         p_conn = parse(conn)
-        params = p_conn.body_params
-        assert params["authentication.entityId"] == "some_secret_entity_id"
-        assert params["authentication.password"] == "some_secret_password"
-        assert params["authentication.userId"] == "some_secret_user_id"
+        headers = p_conn.req_headers
+        auth_header = Enum.find(headers, &match?({"authorization", _}, &1))
+        refute is_nil(auth_header)
+        assert {"authorization", "some_secret_password"} == auth_header
         Conn.resp(conn, 200, @auth_success)
       end)