[CAL-3480] Trigger alert when loading a calendar and no availability is loaded at all

[keithwillcode]

Is your proposal related to a problem?

For auditing reasons, having alerts set up that inform org owners/admins that certain team members have their availability completely turned off or blocked will help the owners/admins work with team members to get their availability set correctly.

Describe the solution you'd like

Upon loading a booking page for a user, if the calendar is completely unavailable, send an alert to the configured person. Configurable to be sent to the owner, admin or user in the org.

_CAL-3480

[keithwillcode]

cc @Jaibles for design/UX input