ids

The ids this execution takes: the node's generators, each aggregate type's the one the host configures for it (wow.aggregates.<ctx.agg>.id-generator), fixed ids in the test DSL.

Handling the commit again (a retry, a replay) takes new ones: an id drawn here for an aggregate a derived command creates may be used only for that same creation command, whose request id is the same every time, so the target creates it once and keeps the first id; any other use would see the id change. To leave the id to the target, derive the creation without an id instead.