def auth_values
    add_available_filter 'tt_start_date', :type => :date, :order => 2
    add_available_filter 'tt_booking_issue', :type => :list, :order => 4, :values => Issue.visible.all.collect { |s| [s.subject, s.id.to_s] }
    add_available_filter 'tt_booking_activity', :type => :list, :order => 4, :values => help.shared_activities.map { |s| [s.name, s.name] }