enhance(pxe): Add Network PXE boot option, doc, and examples

[sygibson]

Adds support to the Terraform Provider Proxmox capabilities for PXE booted VMs. Addresses the following reported issues:

• Allow VMs without ISO and Clone #185
• Network install (PXE) of virtual machines prevented by checks #302

The following changes have been made:

• support for the upstream proxmox-api-go PXE feature added at commit 20220113001728-0c6f43a60b62
• allows use of pxe = true in Terraform resource definition, which is exclussive of Clone and ISO modes
• validates the boot options to ensure a Network boot order is set first
• skips the forced ISO evaluation code, when PXE mode is set
• adds a minimal test case
• adds note to "Known Limitations" in main README.md
• adds appropriate documentation for the vm_qemu.md
• updates go.mod and go.sum appropriately
• adds a pxe_example.tf sample

If this PR is accepted, I would ask that a new Release (presumably v2.9.5) be cut, so the requires statements will pull in the right version with the PXE support.

[sygibson]

@mleone87 - thank you for your help with merging the upstream options in to Telemate/proxmox-api-go which I submitted.

Hoping that you can help move this through, tag, and release (presumably v2.9.5) this enhancement.

Much appreciated!

My apologies about the go.mod and go.sum conflicts - I'm not sure what I'm supposed to do with those to prevent the conflicts. I bumped the go.mod to include the upstream commit require:

• github.com/Telmate/proxmox-api-go v0.0.0-20220113001728-0c6f43a60b62

Then did go mod tidy which modified go.sum.

[sygibson]

Ok - corrected the conflicts ... I failed to re-sync my Fork prior to generating the go.mod and go.sum changes. I thought I was working off of the freshest set of changes.

[sygibson]

@mleone87 - I might have fixed the test failures. I am not able to replicate running the tests in my environment, so I'm not certain on that.

[mleone87]

great work!

[sygibson]

@mleone87 - what is the process to have the 2.9.5 release provider made available in the Terraform registry ? Is there something else I need to do to make that happen ? Or am I just being too impatient waiting for it to be pushed up ?

Thank you for your help in ushering this through and being patient with me.

[mleone87]

@mleone87 - what is the process to have the 2.9.5 release provider made available in the Terraform registry ? Is there something else I need to do to make that happen ? Or am I just being too impatient waiting for it to be pushed up ?

Thank you for your help in ushering this through and being patient with me.

Nothing, the release process already creates the assets and terraform already pulls them

[jValdron]

This is problematic for setting up a VM from PXE:

validates the boot options to ensure a Network boot order is set first

We shouldn't need to have network boot as the first option. Having boot to disk, then PXE, makes sense when you need to do an initial install of a VM through PXE, but want boot directly from disk afterwards.

[sygibson]

@jValdron - a commit has already been made to adjust the validation to check that "network" exists "somewhere" in the boot order, but is no longer required as the first option.

In our use cases, Network is always first, and out infrastructure automation always controls what the Node or Machine should boot to on next boot. This allows the automation to boot systems, and take back control for things like BIOS updates, Firmware updates, decommissioning, recommissioning, audit compliance checks, maintenance break/fix reasons, etc.