Introduced Physical Ticket

Added PhysicalTicket model and controller. It holds the information about each physical ticket bought at the purchase. Physical Tickets are created after every successfull payment.

app/controllers/physical_ticket_controller.rb

@@ -0,0 +1,12 @@
+class PhysicalTicketController < ApplicationController
+  before_action :authenticate_user!
+  load_resource :conference, find_by: :short_title
+  load_and_authorize_resource
+  authorize_resource :conference_registrations, class: Registration
+
+  def index
+    @physical_tickets = current_user.physical_tickets.by_conference(@conference)
+  end
+
+  def show; end
+end