The command `pvesh get cluster/backup` returns a list of defined backups in the following format:
200 OK
[
{
"compress" : "lzo",
"dow" : "mon,tue,wed,thu,fri,sat,sun",
"enabled" : "",
"id" : "7d3875b8db02bfcb258d1904f0c6745af64db4ea:1",
"mailnotification" ...