Users can't tell whether their spaces are recoverable

[travis]

We should tell users if their spaces don't have recovery proofs registered with our service.

We can probably do this by claiming delegations and looking for a matching recovery proof.

[travis]

Note that we may not be able to help the user in the case where we don't have proofs - we don't hold on to Space keys so they can't create a recovery delegation after the Space creation flow is completed.