added optional route formatting feature

[gatopanx]

Solves #1058 #591 #257 #159.

For when you have an implicit way of accessing a namespace (headers, subdomain, or other)

My use case is:

  # NOTE: api.yourapplication.test
  namespace :api, path: '', constraints: { subdomain: 'api' ) } do
    namespace :v1 do
      # ...
    end
  end

I created a custom route formatter class:

module YourApplication
  class CustomRouteFormatter < JSONAPI::RouteFormatter
    class << self
      def format(route)
        return if route == 'api'
        super
      end

      def unformat(formatted_route)
        super
      end
    end
  end
end

and referenced it in my base controller:

      def route_formatter
        YourApplication::CustomRouteFormatter
      end

[lgebhardt]

@gatopan Thanks!