With the new release of Objects (Objects) 2.2, now you can assign a quota policy to a user which enables Objects to set soft thresholds on the number of buckets created by the user within an object store.

Release notes - 

https://portal.nutanix.com/page/documents/details/?targetId=Release-Notes-Objects-v2_2%3Av22-whats-new-r.html

Documented steps -

https://portal.nutanix.com/page/documents/details?targetId=Objects-v2_2:v22-assign-quota-policy-t.html

If you want to know more about Objects

https://portal.nutanix.com/page/documents/details?targetId=Objects-v2_0:Objects-v2_0

ENABLING OBJECTS https://portal.nutanix.com/page/documents/details?targetId=Objects-v2_0:v20-enable-objects-t.html#ntask_t1y_mzc_4hb