Add validation on instance create

[edlerd]

Done

• added instance creation validation:
• for missing root storage
• missing network device name and
• missing storage volume path

Fixes #485

QA

1. Run the LXD-UI:
   • On the demo server via the link posted by @webteam-app below. This is only available for PRs created by collaborators of the repo. Ask @lorumic or @edlerd for access.
   • With a local copy of this branch, run as described here.
2. Perform the following QA steps:
   • Create an instance without root storage
   • Create an instance with a network device that has no name
   • Create an instance with a custom storage volume that has no mount point

[webteam-app]

Demo starting at https://lxd-ui-507.demos.haus

[edlerd]

Hey @piperdeck
I played a bit with your ideas for this and have another iteration ready.

See updated demo link above or the screencast link below for how it is now:

Screencast.from.17.11.2023.13.39.19.webm

Edit: I avoided moving the root storage to the main page of the form, because it would be hidden all the way on the bottom and look a little odd there with the table like view next to the regular form elements.

[piperdeck]

Discovered another area where we should catch missing information in instance config.

When you create a network device for an instance, it enforces giving the network a name but doesn't actually enforce choosing a network for that network device. It lets you click "save changes" but then throws an error. We should make the "Network" field mandatory as well.

[edlerd]

When you create a network device for an instance, it enforces giving the network a name but doesn't actually enforce choosing a network for that network device. It lets you click "save changes" but then throws an error. We should make the "Network" field mandatory as well.

Good point! I think the solution is to auto-select the 1st network when a network is added. That way, the Network selector can't be in an invalid state. I just pushed a change to do that. Please give the PR another pass @piperdeck

[piperdeck]

LGTM

[mas-who]

QA and code both looks good to me