Authorize user action on a given resource.

user is extracted from conn struct based on user configuration (see configuration section in Gardien module docs).

Returns true when user is authorized and false otherwise.

Example:

# in view
defmodule MyApplication.PostView do
  import Gardien.View, only: [authorize?: 3]
end

# in template
<%= if authorize?(post, :delete, @conn) do %>
  <%= link "Delete", to: post_path(@conn, :delete, post), method: :delete %>
<% end %>