fix: Fix stale append_tolerations when removed from the terraform configuration

[skanakal]

Addresses #2207

Description

The provider currently omits append_tolerations from the rancher api payload when the terraform list becomes empty because the expander gates assignment n len(v) > 0, this prevents rancher from receiving an explicit empty list and causes stale tolerations to persist on the cluster spec.

so removing the length guard and preserves field presence whenever the terraform key exists. This allows the provider to serializes explicit empty slices and enables proper removal for append_tolerations

Testing

• Add appened_tolerations
• modify existing tolerations
• remove tolerations while keeping the other fields like memory
• remove entire block

Not a breaking change.

[matttrach]

What happens if you don't include the append_tolerations in your config with this change? Will it unexpectedly clear them out? Wouldn't that be a breaking change for existing configurations?

[matttrach]

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[skanakal]

What happens if you don't include the append_tolerations in your config with this change? Will it unexpectedly clear them out? Wouldn't that be a breaking change for existing configurations?

Here is the current schema, https://github.com/rancher/terraform-provider-rancher2/blob/main/rancher2/schema_agent_deployment_customization.go#L37-L43

"append_tolerations": {
			Type:        schema.TypeList,
			Description: "User-defined tolerations to append to agent",
			Optional:    true,
			Elem: &schema.Resource{
				Schema: tolerationFields(),
			},
		},

Do you mean even though the current schema suggests they are distinguishable, this relies on terraform behavior rather than explicit state comparison...