provider: Support multiple URLs in remote

[maveonair]

Fixes #449

---

This PR updates the provider to use Incus v7 and supports the new multiple remote address model introduced by Incus.

Incus remotes now expose addresses as a list, allowing clustered remotes to define more than one endpoint. To keep the Terraform provider API backward-compatible, the provider continues to use the existing remote.address attribute.

Multiple remote addresses can now be provided as a comma-separated string, matching the Incus CLI configuration format.

provider "incus" {
  accept_remote_certificate    = true
  generate_client_certificates = false

  default_remote = "cluster"

  remote {
    name    = "cluster"
    address = "https://10.1.2.8,https://10.1.2.9"
  }

  remote {
    name     = "docker"
    address  = "https://docker.io"
    protocol = "oci"
    public   = true
  }
}

[stgraber]

@maveonair hmm, can we:

• Split the v6 => v7 into its own commit
• Not break API, either by allowing comma separated values in the existing config key (same as Incus does in its .yml) OR by retaining support for the existing key as a backward compatibility mechanism (returning an error if both are set)

Otherwise, we'll need a major version bump on this one as it's likely to affect quite a few users.

[maveonair]

@maveonair hmm, can we:

* Split the v6 => v7 into its own commit

* Not break API, either by allowing comma separated values in the existing config key (same as Incus does in its .yml) OR by retaining support for the existing key as a backward compatibility mechanism (returning an error if both are set)

Otherwise, we'll need a major version bump on this one as it's likely to affect quite a few users.

1. Yes, I can do that
2. We can do addr = "https://....:8443, https://...:8443" as we have the logic already in place for INCUS_REMOTE. I think both addr and addrs is not a nice dev UX. Would you be fine if we go first with the comma separated approach?

[stgraber]

We can do addr = "https://....:8443, https://...:8443" as we have the logic already in place for INCUS_REMOTE. I think both addr and addrs is not a nice dev UX. Would you be fine if we go first with the comma separated approach?

yep, comma separate works for me and aligns it with what we do in the Incus CLI as far as the on-disk storage of that data.

[maveonair]

@stgraber it looks like the tests are failing with

 Failed instance creation: Failed getting remote image info: Failed to run:
       skopeo --insecure-policy inspect docker://docker.io/alpine:latest --no-tags:
       exit status 1 (time="2026-06-02T18:28:29Z" level=fatal msg="Error parsing
       image name \"docker://docker.io/alpine:latest\": loading registries
       configuration: loading registries configuration
       \"/etc/containers/registries.conf\": registries.conf must be in v2 format but
       is in v1")

I ran the same tests on my machine and ran the command above with Skopeo direclty and I don't get the error message. Do you have an idea why?

[stgraber]

Probably just Github having a dirty /etc/containers. Maybe have the Github workflow delete that folder?