Add support for bodies other than objects

[phylor]

Closes #183.

TLDR

This adds support for bodies we receive, which are not an object. For example, arrays or plain strings.

Let's say we get the response:

{
  data: [
    { name: 'ride_notifications', channels: ['sms'], type: 'notification_setting' }
  ]
}

You could now parse this with the following model:

class Ioki::Model::Passenger::NotificationSettings
  base 'Array', item_class_name: 'NotificationSetting'
end

Changes

• Up until now all response bodies we parse in ioki-ruby need to be objects (in practice a Hash). We now support arrays and basic types (String, ..) as well.

  For arrays we need to define an item_class_name which specifies the class of the items in the array.

  class Ioki::Model::Passenger::NotificationSettings
    base 'Array', item_class_name: 'NotificationSetting'
  end

  For basic types, we only define the type:

  class Ioki::Model::Passenger::ShuttleColor
    base 'String'
  end

• Note that even if the response is a basic type or an array, ioki-ruby will always return a model inheriting Ioki::Model::Base. This allows for helper methods such as serialize and also allows access to the etag using model._etag.

  model = Ioki::Model::Passenger::NotificationSettings.new([{name: 'ride', channels: ['sms']}], 'etag-123')
  
  model._etag
  # => 'etag-123'
  
  model._raw_attributes
  # => [{name: 'ride', channels: ['sms']}]
  # `#_raw_attributes` returns the input value
  
  model.data
  # => [Ioki::Model::Passenger::NotificationSetting<name='ride' channels=['sms']>]
  # `#data` returns the parsed objects

• New method #data which returns the parsed data. For object responses, it returns #attributes. The #data method should be used in client applications to get the parsed array response.

  model = Ioki::Model::Passenger::Product.new(name: 'MyProduct')
  
  model.attributes
  # => {name: 'MyProduct'}
  
  model.data
  # => {name: 'MyProduct'}

[phylor]

@tom-ioki If you have time, this would be a PR about array bodies. Now supporting etags. Let me know if there are things you imagined differently!

[tom-ioki]

Great work! Love it and thank you 😊