standardize typed error responses across draft, pricing and publish endpoints
reduce contract drift between related flows
keep client-side handling more predictable and consistent
reject duplicate sector and group bindings within draft mutations
harden draft structure consistency at the backend layer
prevent conflicting bindings before they reach publish flow
add stale draft protection for mutation flows
validate referenced entities before applying draft changes
reduce invalid draft writes caused by stale state and broken references
keep mutation behavior explicit and version-aware
