Up to now, a draft/mock implementation was used, relying on a »spec tuple«,
which was fabricated by MockJobTicket. But with the introduction of
NodeGraphAttachment, the MockSequence now generates a nested ExitNode structure,
and thus the JobTicket will be created through the "real" ctor, and
no longer via MockJobTicket.
Thus it is possible to skip this whole interspersed »spec tuple«,
since ExitNode *is* already this aggregated / abstracted Spec
PROBLEM: can not implement Spec-generation, since
- we must use a λ for internal allocation of JobTickets
- but recursive type inference is not possible
Will thus need to abandon the Spec-Tuple and relocate this
traversal-and-generation code into JobTicket itself
Use another unit-test (FixtureSegment_test) to guide and cover
the transition from the existing fake-implementation to the
actual implementation, where the JobTicket will be generated
on-demand, from a NodeGraphAttachment
