[BUG] Can't update any `rancher2_role_template`

[mouellet]

Rancher Server Setup

• Rancher version: v2.8.5
• Installation option (Docker install/Helm Chart):
  • If Helm Chart, Kubernetes Cluster and version (RKE1, RKE2, k3s, EKS, etc): RKE1

Information about the Cluster

• Kubernetes version: v1.28.7
• Cluster Type (Local/Downstream): Local

User Information

• What is the role of the user logged in? (Admin/Cluster Owner/Cluster Member/Project Owner/Project Member/Custom): Admin

Provider Information

• What is the version of the Rancher v2 Terraform Provider in use? v4.2.0
• What is the version of Terraform in use? v1.5.7

Describe the bug

We have custom roles _without external_rules defined_. When terraform-provider-rancher2 to v4.2.0 any update to the a rancher2_role_template resource is blocked by the Rancher Webhook with the following error message:

error: roletemplates.management.cattle.io "rt-p***" could not be patched: admission webhook "rancher.cattle.io.roletemplates.management.cattle.io" denied the request: ExternalRules can't be set in RoleTemplates with external=false

The provider might be sending and empty array value for the externalRules attribute to the rancher API but the Rancher Webhook checks for a nil value. See: https://github.com/rancher/webhook/blob/main/pkg/resources/management.cattle.io/v3/roletemplate/validator.go#L130

To Reproduce

With kubectl, edit a roletemplates by adding externalRules: [] to the manifest.

Actual Result

See error above

Expected Result

Role template should be updated

Screenshots

Additional context

[joesims22]

Validated on v2.10-head id 8b50f83

#	Priority	Description & Link	PASS/FAIL
1	P0	Verify updating RT via TFP is successful	✅ PASS
2	P0	Verify TFP sets external attribute to false by default	✅ PASS
3	P0	Verify external rules value is set to nil if external attribute is not set	✅ PASS
4	P0	Verify external rules cannot be set when updating RT via TFP while external is set to false	✅ PASS
5	P0	Verify external rules can be set when updating RT via TFP after setting external to true	✅ PASS
6	P1	Verify external rules cannot be set via kubectl when external is set to false	✅ PASS
7	P1	Verify external rules can be set when updating RT via kubectl after setting external to true	✅ PASS
8	P0	Verify external rules are removed when external set to false via TFP	✅ PASS
9	P0	Upgrade: Verify updating RT via TFP is successful upon upgrading Rancher	✅ PASS