Prevent end users from asking for product trial

Issue summary

• End users on the site are able to request for product trials if the product does not already exist on the site.
• This sends out an email to the site admin asking to approve the product trial request.
• Site admins do not have any options to disable these request, or to stop the emails from being sent out to them.

Suggested behavior

• Give site admins the options to control these request
  • Option to disable product trial request entirely
  • Or option to not have emails sent out to them for these request.