Description of problem:
Need doc content for following use case: As an admin who uses BlueStore, I need to know how to migrate Ceph storage volumes from Filestore to Bluestore.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
Migration plan outline: bringing offline 1 OSD host with filestore at a time after bringing up a new OSD host with Bluestore. Let the cluster recover, repeat with another OSD host.