Use Forwardable within Message to avoid method boilerplate

[GabrielMalakias]

First of all, thank you for maintaining this gem! I really appreciate your efforts.

While diving into the code I just noticed that a bunch of methods were defined just as a proxy to the data structure.

As I have seen here: https://github.com/ruby-shoryuken/shoryuken/blob/master/lib/shoryuken.rb#L48 I decided to use the SingleForwardable to delegate to the structure directly.

It's a small thing for now but might the beginning of some contributions

[cjlarose]

Thanks for your contribution! Tests are failing. I think you might want to look into Forwardable instead of SingleForwardable.

https://ruby-doc.org/stdlib-2.6.2/libdoc/forwardable/rdoc/Forwardable.html

[GabrielMalakias]

Done

[cjlarose]

Awesome work! Thanks!

[januszm]

A minor thing but skipping the parentheses in this case would match the macro-style methods better and also sorting the lines ascending would make it easier to read, e.g.:

def_delegators :attributes,
               :body,
               :data,
               :md5_of_body,
               :md5_of_message_attributes,
               :message_attributes,
               :message_id,
               :receipt_handle