* There is no auth in Safekeeper HTTP at all currently,
so simply calling `check_permission` is not enough.
* There are no checks of Safekeeper still working with the data,
as "still working" is burry now: a timeline may be "active"
while there are no compute nodes and all data is propagated.
* Still, callmemaybe is deactivated, and timeline is removed from the
internal map. It can easily sneak back in case of race conditions
and implicit creations, though.