Aliases for abilities

[davydovanton]

Something like this:

class Post::Abilities
  include Kan::Abilities

  register('read') { |_, _| true }
  register_alias('alias_read', 'read')
end

abilities = Kan::Application.new(post: Post::Abilities.new)
abilities['post.read'].call(current_user, post)       # => true
abilities['post.alias_read'].call(current_user, post) # => true