Add request helper to reduce duplication.

[asummers]

Coverage went down somehow, though this is the same code, more or less. This also suggests an obvious API change that I would like to propose -- making body be the first argument of Stripe.Request. In the case of e.g. update, it would look like:

  @spec update(String.t, map, map, list, module, Keyword.t) :: {:ok, struct} | {:error, Stripe.api_error_struct}
  def update(endpoint, changes, schema, nullable_keys, module, opts) do
    changes
    |> Changeset.cast(schema, :update, nullable_keys)
    |> Stripe.request(:post, endpoint, %{}, opts)
    |> handle_result(module)
  end

I have this done locally and it looks pretty clean throughout. I can push to this branch if you all want, or a new one. This module would look like: https://gist.github.com/asummers/49384f353da45752b0cbb3ed61cbdc01 with handle_result being public because it is used in Stripe.Card.create/4.

[coveralls]

Coverage decreased (-0.1%) to 26.027% when pulling 87fc391 on asummers:add-request-helper into fab5b57 on code-corps:2.0.

[joshsmith]

@DavidAntaramian could use your eyes on this but I like the proposal above re: changing to have body be first arg.

[joshsmith]

🙌