fix: add support for imported cluster config

[kinarashah]

Issue:

#1523

Problem

Terraform currently does not support setting the ImportedConfig field explicitly. The assumption has been that Rancher creates an imported cluster automatically when no configuration is provided.

However, this assumption no longer holds as a new required field for supporting private registries was introduced for imported clusters. As a result, explicit support for ImportedConfig is now necessary.

Solution

Introduced support for imported_config in rancher2_cluster. As far as I know, imported clusters are not supported with rancher2_cluster2 since these are handled via the v3/clusters endpoint.

The resulting state differs slightly when imported_config is used so added the new state to the expected state list. However, this is consistent with the behavior observed when creating imported clusters directly through the Rancher API. The difference is not significant as the registration URL is correctly generated in both cases and the cluster becomes active after a successful import.

Engineering Testing

Manual testing, created cluster using both old and new format:

resource "rancher2_cluster" "foo" {
  name        = "foo"
}

resource "rancher2_cluster" "bar" {
  name        = "bar"
  imported_config {
    private_registry_url = "test102.io"
  }
}

[matttrach]

Please sign your commits with a verified key.

[matttrach]

What version of the provider is this targeting?
Is this expected for the v8 release correlating to Rancher's v2.12 or something earlier?

[matttrach]

Config is not a valid word for the commit messages, please use "configuration".

[matttrach]

or just "fix: add support for imported cluster" should be fine