Add 'args' as optional configuration parameter when creating a VM

[rhpijnacker]

To create macOS VMs in Proxmox, the args parameter needs to be set to pass some additional values to the underlying KVM. This PR adds support for setting this in the packer source.

This builds on https://github.com/Telmate/proxmox-api-go/pull/117/files, which already makes it possible to pass Args in the ConfigQemu struct.

Closes #243

[hashicorp-cla]

All committers have signed the CLA.

[rhpijnacker]

I tested this by deploying a VM that includes the args= property.
I'm not sure what kind of unit test to add.

[lbajolet-hashicorp]

Hi @rhpijnacker,

Thanks for the PR! I left a few comments which err more on the nitpick side of things than anything else, the code itself looks good to me.
To be sure, have you tested those changes locally? Does it work as you would expect? Nevermind this, I just saw your second message, all clear here, I don't think there's a lot of tests for this plugin already (might be good to have some eventually) so I would think we'll rely on good will and manual testing for now.

[lbajolet-hashicorp]

Out of curiosity, is the space in front of no-reboot voluntary or is it a typo? If it is intended, I would suggest documenting it clearly so users aren't surprised in case they don't add one and it fails unexpectedly?

[rhpijnacker]

There is no reason for that space. Removed it.

[lbajolet-hashicorp]

Bit nitpicky on my part, but just for clarity, since this is for extra raw args, and since this is for advanced use-cases only, I would suggest making the name more explicit here, something along the lines of qemu_extra_args.

[rhpijnacker]

Sure. Renamed it to qemu_additional_args (to stay consistent with e.g. additional_iso_files).
Renamed the internal structure-property to AdditionalArgs.

[rhpijnacker]

FYI: Succesfully tested it manually with the new name.

[lbajolet-hashicorp]

Thanks for the reroll @rhpijnacker!

This looks good to me, I'll merge this PR now.

[lbajolet-hashicorp]

FYI: CI was complaining that the generated code differed, I presume you had amended the docs and hcl2spec files manually?
If you want to contribute to the plugin later, I suggest using the make generate target for this, we're using a tool from our SDK to generate the docs partials and the hcl2spec files from the Go code so we don't need to manually maintain those.

I've pushed the change on your branch, on top of your commits, so we can merge this now.