Prevent changing the work status back to forthcoming/cancelled/postponed once it's active

[ja573]

[tosteiner]

A cautious note: if we could add a warning of sorts to the selection process indicating that a switch to "Active" will be irrevertible, that would be really useful, as I can already see publishers getting in touch with us to ask for changes because they just wanted to try it out ...

[brendan-oconnell]

@ja573 I assume we still want superusers to be able to change the work status back to forthcoming/cancelled/postponed once it's been set as active? Just want to confirm.

[ja573]

@ja573 I assume we still want superusers to be able to change the work status back to forthcoming/cancelled/postponed once it's been set as active? Just want to confirm.

Yes