Apply customer edit reviews (v4)

Save a bulk edit review as approved, up to 20 customers per call (apply more in parts, each standing alone), in one transaction: each named customer gets one version holding exactly the reviewed changes and the member's overrides (keyed as business_customers_update_v4 takes them, name excepted; the household as counts) and joins its labels, missing ones created. The review is a business_customer_edit_reviews_create_v5 run or one its version 4 started. Edits follow business_customers_update_v4's rules, each customer's outcome naming the fields they set; a value its buyer type lacks is INVALID_INPUT (CUSTOMER_VERSION_ATTRIBUTE_NOT_APPLICABLE, naming the customer): remove it, apply again. STALE_WRITE saves nothing when a customer or option changed since (review again) or the review predates the customer model (review_before_customer_model: propose again). Each new version reruns its customer as business_customers_update_v4 describes; labels alone make no version.