Namespaced (with custom path option) and scoped routes support

My API endpoints are defined like that:

namespace :api, path: '' do
  scope ':customer' do
    api_version(module: 'V1', header: { ... }) do # versionist gem
      jsonapi_resources :users
    end
  end
end

This ends up with routes looking like:
/:customer/users/:id
but JR returns self links like:
/api/v1/users/:id

I managed to fixing that by monkey-patching JSONAPI::ResourceSerializer with:

module JSONAPI
  class ResourceSerializer
    def formatted_module_path(source)
      "#{currrent_customer}/"
    end
  end
end

but it's less than ideal. It would be nice to have a proper support for custom routes.

It could be fixed by #159 maybe.

Thanks!

Start with JSONAPI::ResourceSerializer and its formatted_module_path method, which the issue identifies as the current workaround. Review the custom namespace and scope routes in the example and issue #159, then verify that generated self links match the routed /:customer/users/:id path without monkey-patching.