Install LXD as a prerequisite when installing microcloud snap

[dwbfox]

When installing and initializing Microcloud, it should be able to also download and configure the required LXD snap rather than leaving it up to the user to configure. This would also prevent the possibility of incompatible LXD versions being used with Microcloud (if such limitations should arise)

Right now, installing the microcloud snap and running init of course returns an error

$ sudo microcloud init
Waiting for services to start ...
Error: Failed waiting for LXD to start:

The request is for this to be avoided altogether. At the very least it should give the user a more friendly error to indicate that it doesn't detect LXD as running/installed.

[roosterfish]

When installing and initializing Microcloud, it should be able to also download and configure the required LXD snap rather than leaving it up to the user to configure

The microcloud snap doesn't have permission to do this. It's the users responsibility to download the snaps before running init.
We clearly state in the docs that all snaps need to be installed together. If you find a spot where this isn't the case, please report.

Just wanted to reproduce the error, can you confirm it's showing the deadline exceeded message:

root@micro01:~# microcloud init
Waiting for services to start ...
⨯ Error: Failed waiting for LXD to start: Get "http://unix.socket/internal/ready": context deadline exceeded

Which version of MicroCloud are you using? Please share snap list.

IIRC there was a case in the past where we saw LXD's unix socket not to be present right away, likely caused by LXD starting up. Therefore MicroCloud currently waits for the socket to be present and the /internal/ready endpoint to be responding, all within the same context deadline.