Function on_object_mutation 

pub fn on_object_mutation(
    profile: &ProfileId,
    bucket: &BucketId,
    prefix: &str,
    object_key: Option<&ObjectKey>,
    store: &CacheHandle,
)

Invalidate Objects and ObjectHead keys for the affected scope when an object is created, updated, deleted, or moved within bucket/prefix.

Callers pass the exact prefix that was mutated. If the mutation spans multiple prefixes (e.g. a recursive delete), callers are responsible for calling this helper once per distinct prefix.