Better maintenance window behaviour (maintenance status)#562

Currently the behavior is (or appears to be to me) that whatever a monitor’s status is prior to the start of a maintenance window is what the status remains at through the entire maintence window period.

I propose continuing to check the status of each monitor, BUT with the following behavior:
-if the monitor goes DOWN during the maintenance window, status would check to something along the lines of ‘SCHEDULED DOWN” (perhaps with a yellow color?). Uptime stats would NOT be affected by this [new] status label (i.e. in current logic, this status would be considered the same as ‘UP’). The dashboard (and status pages, for end user visibility) would report the down event (with the new status label) to denote the difference between this new status, down but planned, and an unplanned down event). No alerts would be sent for this new down event.
-If a monitor goes UP during the maintenance window, status would return to “UP”/green. If the prior status were DOWN (which would indicate an outage/down event which started PRIOR to the maint window), then uptime stats would accrue uptime. Alert contacts which would normally receive up event noticeswould still receive the up event notice.

In short: add a new status for down, but during a maintencnace window.