Example, non-working, attempt to use nesteed mounts in Grape for DRY design with multiple paths to same resources

app.rb

require "grape"
# Example attempt to do nested mounting. The real-world case is for a resource which can be
# addressed in multiple ways, and I want a DRY design where groups define the parameters to address
# an item, but the manipulations possible are the same, and defined by the http verb, so should be
# in one place (class Thing in this example to read a "thing" resource)

class Thing < Grape::API
  get do
    { :message => 'You found the thing!' }
  end
end

class Things < Grape::API
  group :by_name do
    mount Thing
  end

  group :by_id do
    mount Thing
  end
end

class MainService < Grape::API
  prefix      'api'
  version     'v2'
  format      :json
  rescue_from :all

  group :things do
    mount Things

    # This isn't necessary for the example, just demonstrates that this is otherwise valid Grape code
    get do
      [:by_id, :by_name]
    end
  end
end