Enable pods to close down 'gracefully'

[goobertron]

When a podmin wishes to close down their pod permanently, there should be an option for them to do so in a way that will remove all connections on remote pods.

This would include closing down any sharing connections with accounts on the pod that is closing by accounts on all other pods.

Ideally, there would be a button that a podmin would press that says 'I wish to close down my pod permanently', and doing so would send out notifications to all remote pods that they should forget about this pod in federation and should also remove sharing relationships with all accounts on that pod.

I notice this because the diaspora* HQ account has thousands of sharing relationships with accounts on pods that are no longer operational – this becomes clear when their 'birthdays' come around.

I hope what I've written makes sense and is achievable