Apply default scheduled maintenance to all instances in a team tier

[knolleary]

Description

The work done via #6079 allows an admin to set a default schedule for maintenance restarts for instances in a given team tier.

When a new instance is created, it gets a slot from the default schedule applied to its settings. Existing instances however do not get the option applied.

The goal of this task is to apply the default to all instances in the tier.

My proposed solution is:

A new task runs once a day, looks for any instances belonging to a TeamType that has maintenance defaults but the instance doesn't have their own setting enabled. It can then assign a slot to the instances. This has the benefit of allowing the default to be a bigger time window and the instances get distributed within it.

We will need to refine the exact criteria for enabling the flag; it should only apply if the TeamType config disallows disabling the schedule.

This will catch-up the backlog, but also handle cases where a team downgrades to Starter following a Pro trial and will ensure its instances get the maintenance schedule applied.

The downside of this is that if the default schedule is changed or turned off etc, it won't apply that change to the existing instances.

Epic/Story

No response

Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate