feat: Add all-current-oncall-engineers

[samuel-form3]

In order to alert all the engineers of a company we're adding a new slack group called:

all-current-oncall-engineers

[TiPPeX2]

Can we add some configurations(to disable) for this? I also thought about adding a configuration for the prefix of the schedule.

Maybe if you could assist I'd add it(no go familiarity but if you can write what to do, it I think I can do it)