Backport #12164
This PR extends the notifications API to allow specific notification statuses to be searched for and to allow setting of notifications to statuses other than read.
By default unread and pinned statuses will be returned when querying for notifications - however pinned statuses will not be marked as read.
Close#12152
Signed-off-by: Andrew Thornton art27@cantab.net
* introduce GET /notifications/new
* add TEST
* use Sprintf instead of path.Join
* Error more verbose
* return number of notifications if unreaded exist
* 200 http status for available notifications