feat(notification/rule): add JSON body for the HTTP POST (#14994)
The body of the JSON webhook would be:
{
"version": 1,
"rule_name": notification._notification_rule_name,
"rule_id": notification._notification_rule_id,
"endpoint_name": notification._notification_endpoint_name,
"endpoint_id": notification._notification_endpoint_id,
"check_name": r._check_name,
"check_id": r._check_id,
"check_type": r._type,
"source_measurement": r._source_measurement,
"source_timestamp": r._source_timestamp,
"level": r._level,
"message": r._message,
}