Show recipient on notification page
Show recipient on notification page

Since we removed the notifications table from this page we need a
different way of showing who the message was sent to.

Our `Template` classes already have a way of doing this, and we have a
flag to switch this on (which is what this PR changes).

gov-cjwaszczuk/notifications-admin,alphagov/notifications-admin,alphagov/notifications-admin,alphagov/notifications-admin,gov-cjwaszczuk/notifications-admin,gov-cjwaszczuk/notifications-admin,alphagov/notifications-admin,gov-cjwaszczuk/notifications-admin