Immediate deletion destroys master key material outright, and every
object encrypted under that key becomes permanently unreadable. The
delete endpoint accepted that request as a query parameter, which is the
form most easily issued by accident and the one that made the waiting
window bypassable.
The query string can now only schedule a deletion: `force_immediate`
with any value other than `false`, or a `confirm_key_id` parameter, is
refused with 400 rather than downgraded to a scheduled deletion, so a
caller cannot read the answer as "destroyed". The JSON body form is
unchanged and remains the single way to reach the service gate that
enforces the server opt-in and the echoed confirmation.
Classify the route accordingly: `RouteRiskLevel` gains `Critical` for
routes whose worst case is permanent loss of user data, and the KMS key
deletion route is the only member, pinned in both directions by a matrix
test. Endpoint-level coverage for the 7-30 day window bound is added for
every configured backend.
Refs rustfs/backlog#1585 (part of rustfs/backlog#1562)
Zhengchao An