If sharer receives Accept on an Offer/Dep where the sharer hosts the child
ticket, it records a RemoteTicketDependency and runs inbox forwarding to ticket
followers. But this relies on a TicketDependencyOffer record already existing.
I'll take care of that in the next patches.
sharerAcceptF and sharerRejectF now use the insertToInbox from
Vervis.Federation.Util instead of their own copies of it, which were identical
anyway. Perhaps gradually all the inbox insertion in all S2S handlers will
switch to using that function.
