Add "port" parameter to the "graphics" schema

[khmarochos]

Summary

Add support for custom port configuration in VNC graphics for libvirt domains. This feature allows users to specify a fixed port number for VNC connections instead of relying on automatic port assignment.

Changes

• Add port parameter to graphics schema: Optional string parameter with numeric validation
• Implement validation constraints: Port parameter can only be used with VNC graphics type and requires autoport = false
• Update domain XML generation: Properly handles port configuration in libvirt XML, defaults to -1 when not specified
• Add comprehensive tests: Covers both successful configuration and validation error cases

Usage Example

resource "libvirt_domain" "example" {
  name = "example-domain"
  graphics {
    type     = "vnc"
    autoport = false
    port     = "5900"
  }
}

Validation Rules

• Port parameter is only valid when type = "vnc"
• When port is specified, autoport must be false
• Port value must be a valid numeric string
• Configuration errors provide clear validation messages

Test Coverage

• TestAccLibvirtDomain_GraphicsVNCPort: Tests successful VNC port configuration
• TestAccLibvirtDomain_GraphicsVNCPortValidation: Tests validation scenarios including invalid type, autoport conflicts, and non-numeric values

Backward Compatibility

This change is fully backward compatible. Existing configurations continue to work unchanged, and the new port parameter is optional.

[khmarochos]

The related feature request is #1182.

[dmacvicar]

ℹ️ ℹ️ ℹ️ ℹ️ ℹ️ ℹ️

This contribution is relevant to the legacy version of the provider, which is now in the v0.8 branch of this repository.

Future development is based on a new provider, which is not compatible with this one, nor does share code.

As the new provider solves many issues with the legacy, and to make development in my free time more enjoyable, I have decided to close all PRs for the legacy provider, and to ask to check if the contribution would apply to the new one. This also to encourage trying the new version.

• https://registry.terraform.io/providers/dmacvicar/libvirt/latest

and check the documentation:

• https://github.com/dmacvicar/terraform-provider-libvirt/blob/main/README.md
• https://registry.terraform.io/providers/dmacvicar/libvirt/latest/docs

You are free to reopen the PR for v0.8, which is targetted now to the v0.8 branch. We may also start a discussion if we can assemble a team of maintainters for the legacy branch. My efforts will go into the new provider.

I ask you to check the new provider and re-evaluate this contribution. 🙏