Square brackets around IPv6 addresses in ceph.conf

[boltmark]

Issue report

What version of MicroCeph are you using?

latest/edge (19.2.0~git+snapbfd2c916c8)

What are the steps to reproduce this issue ?

See canonical/microcloud#380 for the steps taken to produce the error (during microcloud init questionnaire, set up CephFS and use IPv6).

Can also see a similar failure when setting up LXD with a CephFS storage pool via MicroCeph:

1. Create VM

lxc init ubuntu-minimal:24.04 v1 --vm -c limits.cpu=2 -c limits.memory=4GiB

2. Add volume to be used as disk

lxc storage volume create default disk1 size=5GiB --type=block
lxc config device add v1 disk1 disk pool=default source=disk1

3. Start VM and note IPv6 for enp5s0

lxc start v1
lxc ls v1

4. Enter VM and install MicroCeph and LXD

lxc exec v1 bash
snap install lxd --channel latest/edge
snap install microceph --channel latest/edge

5. Bootstrap MicroCeph with IPv6 address saved from above. Set up a new cluster, and add the disk created above

microceph init

6. Allow fewer than 3 disks for the sake of the reproducer

microceph pool set-rf "" --size=1

7. Initialize LXD and attempt to create CephFS storage pool

lxd init
lxc storage create lxd_cephfs cephfs cephfs.create_missing=true cephfs.meta_pool=lxd_cephfs_meta cephfs.data_pool=lxd_cephfs_data source=lxd_cephfs

What happens (observed behaviour) ?

As per canonical/microcloud#380, failure to mount error is observed:
Error: Failed to mount "fd42:4c88:a791:d989:216:3eff:fe97:243c:6789,fd42:4c88:a791:d989:216:3eff:fe6d:c28e:6789:/" on "/tmp/lxd_cephfs_3143952555/mount" using "ceph": invalid argument

Additional comments.

See this MicroCloud comment -- should ceph.conf use square brackets around IPv6 addresses? I'm unable to find official documentation requiring this, but LXD expects this and this blog post seems to imply that square brackets are needed.