[Wishlist] Configure storage tiers provided by Ceph

Today, when deploying Cinder through a Private Cloud Build, it is not possible to get different storage tiers. We can only get one storage tier served by Ceph.

As a end-user, I might to be able to choose on which storage tier I want to place my VMs (e.g. regular, low-end, fast, only-SSD, ...). In order to do that, I will choose the appropriate volume type to use when creating my volume [0].

As an administrator, I want to be able to create different pools in Ceph and assign the appropriate OSDs to those pools. For example, I would like to create a pool that will use only my SSD OSDs and another pool that would use only bcache backed HDDs. Therefore, I can offer two different storage tiers to my OpenStack users.

As an administrator, I want to be able to create different backends in Cinder for my users to target them as volume types [1].

[0] https://docs.openstack.org/cinder/latest/admin/blockstorage-multi-backend.html#usage
[1] https://docs.openstack.org/cinder/latest/admin/blockstorage-multi-backend.html this but with Ceph instead of LVM.