Acknowledgement returned by all relationship write endpoints.Carries the edge_handle — the backend-opaque handle that identifies the
relationship (correlation_id under DbBackend, edge_id under NextBackend) and
is fed back into retype/reweight/fold. Future revisions may add the
projected edge id or event id.
{
"edge_handle": "bb448575-c4c7-45c7-a1a2-a9946535e7cb"
}