Expose Ceph OSD pool config options

[luissimas]

Description

When integrating with Ceph, the charm requests the creation of a new OSD pool in the Ceph cluster by exchanging relation data with the ceph-mon charm. We currently don't provide any way to configure the creation of that OSD pool, but ceph-mon accepts some extra parameters on the relation data that should allow us to set some options.

The charm should expose config options that will be used to configure the Ceph OSD pool at the moment of its creation. Those config options will have an effect only when the pool is being created, and subsequent alterations should not have an effect on an already created OSD pool.

Since the Ceph integration was highly inspired by the cinder-ceph charm, we can use it as a reference to see what config options are available and how to apply them to the relation data.

Definition of done

• The charm exposes several config options that, when defined, are supplied to the ceph-client relation data to configure the creation of the OSD pool

Resources

https://charmhub.io/cinder-ceph/configurations
https://opendev.org/openstack/charm-cinder-ceph/src/branch/master/hooks/cinder_hooks.py#L122
https://linuxcontainers.org/incus/docs/main/reference/storage_ceph/#limitations