Recent Veeam is very picky about storage class names. Add `_MINIO_VEEAM_FORCE_SC` env var.
It will override the storage class returned by the storage backend if it is non-standard
and we detect a Veeam client by checking the User Agent.
Applies to HeadObject/GetObject/ListObject*
canceled callers might linger around longer,
can potentially overwhelm the system. Instead
provider a caller context and canceled callers
don't hold on to them.
Bonus: we have no reason to cache errors, we should
never cache errors otherwise we can potentially have
quorum errors creeping in unexpectedly. We should
let the cache when invalidating hit the actual resources
instead.
