feat(room_at_capacity_mailer): [PPT-1721|PPT-1852] notify when people_count equals or exceeds capacity

[chillfox]

No description provided.

[stakach]

This will send an email every 20 seconds while the room is at capacity
We probably want to do 2 things:

1. track where rooms are at or over capacity (system_id => over_capactity_detected_count)
   increment the count every poll
2. only send an email when the over_capactity_detected_count == 2 (i.e. 5min polling means email sent when over capacity for 10min)
3. if a room drops below capacity then delete the system_id from the hash or set to 0

We might also want to ensure only one email is sent per meeting?
but i think the above should work well enough

[chillfox]

There is a debounce_time_minutes option that limits how frequently notifications can go out for the same system.
requiring it to be over for multiple checks is a good idea, I will add that now.

[stakach]

minor change

[stakach]

LGTM