Add attributes presets

[Bhacaz]

The idea is to able to define a subset/preset/view of attributes. It may reduce the number of if are very similaire Serializer class to define.

Example

class UserSerializer
  include BrightSerializer::Serializer
  attributes :id, :name

  view :edit do
    attribute :email, :updated_at, :created_at
  end
end

UserSerializer.new(User.all).serializable_hash
# => {:id=>1, :name=>"John"}
UserSerializer.new(User.find(1), view: :edit).serializable_hash
# => {:id=>1, :name=>"John", :email=>"[email protected]", :updated_at=>"2020-06-21T20:51:10.000Z", :created_at=>"2020-06-21T20:51:10.000Z"}

Idea from https://github.com/procore/blueprinter