Description of problem:

In keystone v3, we need to add the following in ceph.conf:

'rgw_keystone_implicit tenants = true' This creates buckets under tenant namespace. 
'rgw_swift_account_in_url = true' Gets the tenant name from endpoint.

The endpoint should end with 'AUTH_%(tenant_id)s' in its url:

$openstack endpoint set --url 'http://localhost:8000/swift/v1/AUTH_%(tenant_id)s'

Doc link:

https://access.redhat.com/documentation/en-us/red_hat_ceph_storage/3/html/using_keystone_to_authenticate_ceph_object_gateway_users/configuring_the_ceph_object_gateway

Related BZ:
https://bugzilla.redhat.com/show_bug.cgi?id=1699206