Prepares for cloning a specified subscriber node.
This duplicates the ‘provider’ node's configuration under a new node ID in preparation for
the node to be copied via standard database tools.
Note that in order that we be certain that this new node be consistent with all nodes, it
is important to issue a SYNC event against every node aside from the provider and wait to
start copying the provider database at least until all those SYNC events have been con‐
firmed by the provider. Otherwise, it is possible for the clone to miss some events.