Filter Alerts by [time of day] and [day of week]

### Problem Statement

We'd like to get informed on slow average query times, but **only in certain time ranges**.

We know from our previous APM tool that many alerts came in unnecessarily because the _average_ response time of our servers was very high because of very few requests *at night*.
E.g. a single customer generating two documents at 3 am in the morning drove up the average time altough it wasn't overburdening our servers; it just takes 10-15 seconds to generate each one.

### Solution Brainstorm

We'd like to filter alerts so that they are only triggered if...
* ...the average response time is > 2000 ms and
* ...this occurs between 7am and 8pm on a weekday

### Product Area

Alerts