Import Routes Into Dispatch Plan

Take up to 1,500 whole undispatched routes per request into the plan's draft, archiving each live source route; its orders join the plan. Routes the plan already took are reported as unchanged, so a retry is safe. The whole selection is refused when any id is unknown or ineligible (400 PLAN_SELECTION_INVALID, naming the ids) or another plan holds one of its orders (409 ORDER_HELD_BY_PLAN). More ids than one request takes fail with 422 VALIDATION_ERRORS. A plan holds at most 22,000 orders, 1,500 routes and 24,000 stops; an import that would grow it past them is refused with 400 PLAN_DOCUMENT_INVALID. Fails with 409 PLAN_LEASE_HELD (naming heldBy) while anyone has the plan open in the Planner, and with 409 PLAN_REVISION_STALE (naming currentRevision) when the plan changed since expectedRevision.