The only way to move an Assignment to a new employee was two separate calls
(PATCH return + POST create), which is not atomic and left a race window
where a third party could grab the now-in_stock AssetItem in between, plus
no rollback if the second call failed. Adds transferAssignment() which
closes the old Assignment and creates the new one inside a single
prisma.$transaction(), per docs/asset-license-management.md's "Assignment
(chốt 2026-08-02)" spec. Does not touch AssetItem.status or
License.seatsUsed — the resource never becomes free mid-transfer. Wired
into PATCH /api/assignments/[id]: an employeeId key in the body dispatches
to transfer, a returnedAt key to return, both together is rejected as
mutually exclusive.
POST/GET /api/assignments mirror the existing entity route pattern
(auth-gated, thin handler delegating to src/lib/assignments.ts). PATCH
/api/assignments/[id] is the first dynamic-segment route in the codebase,
per the stakeholder-confirmed convention (docs/asset-license-management.md)
of update routes being PATCH /api/<entity>/[id] rather than an
action-based sub-route.
toanhoang