feat(kubernetes): add support to configure control plane firewall

[basert]

This PR allows to configure https://docs.digitalocean.com/products/kubernetes/how-to/add-control-plane-firewall/

[loosla]

@basert Fabian, Thanks again for a great contribution 🚀
I left some suggestions that should allow acceptance tests to pass.
The rest looks great! Ready to approve when we fix the tests 🙂

[basert]

@basert Fabian, Thanks again for a great contribution 🚀 I left some suggestions that should allow acceptance tests to pass. The rest looks great! Ready to approve when we fix the tests 🙂

Uhh, I don't see any of your suggestions :) Can I see the test results? I only have access to our company DO account and I dont wanna run the tests against that environment.

[loosla]

@basert Hey Fabio, Sorry, I forgot to complete the review, which caused the comments to remain in the pending stage. I appreciate you bringing this to my attention. You should now be able to see the suggestions.
Thanks for your help in improving the DO Terraform provider! 🐬
Here is the current acceptance tests output:

=== RUN   TestAccDigitalOceanKubernetesCluster_ControlPlaneFirewall
=== PAUSE TestAccDigitalOceanKubernetesCluster_ControlPlaneFirewall
=== CONT  TestAccDigitalOceanKubernetesCluster_ControlPlaneFirewall
panic: control_plane_firewall: '': source data must be an array or slice, got map

goroutine 332 [running]:
github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema.(*ResourceData).Set(0xc000b89400, {0x123b421, 0x16}, {0x10b6180, 0xc000cb2330})
	/home/terraform-provider-digitalocean/vendor/github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema/resource_data.go:230 +0x2ae
github.com/digitalocean/terraform-provider-digitalocean/digitalocean/kubernetes.digitaloceanKubernetesClusterRead(0xc000bfd188, 0xc000bd45a0, 0xc000b89400)
	/home/terraform-provider-digitalocean/digitalocean/kubernetes/resource_kubernetes_cluster.go:423 +0x827

[basert]

@basert Hey Fabio, Sorry, I forgot to complete the review, which caused the comments to remain in the pending stage. I appreciate you bringing this to my attention. You should now be able to see the suggestions. Thanks for your help in improving the DO Terraform provider! 🐬 Here is the current acceptance tests output:

=== RUN   TestAccDigitalOceanKubernetesCluster_ControlPlaneFirewall
=== PAUSE TestAccDigitalOceanKubernetesCluster_ControlPlaneFirewall
=== CONT  TestAccDigitalOceanKubernetesCluster_ControlPlaneFirewall
panic: control_plane_firewall: '': source data must be an array or slice, got map

goroutine 332 [running]:
github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema.(*ResourceData).Set(0xc000b89400, {0x123b421, 0x16}, {0x10b6180, 0xc000cb2330})
	/home/terraform-provider-digitalocean/vendor/github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema/resource_data.go:230 +0x2ae
github.com/digitalocean/terraform-provider-digitalocean/digitalocean/kubernetes.digitaloceanKubernetesClusterRead(0xc000bfd188, 0xc000bd45a0, 0xc000b89400)
	/home/terraform-provider-digitalocean/digitalocean/kubernetes/resource_kubernetes_cluster.go:423 +0x827

Awesome, thanks for the review, I adjusted the code to your suggestions.

[loosla]

Looks awesome! Thanks for doing an amazing job! 🚀 🦈

[loosla]

@basert Your changes are in v2.48.1 v2.48.2 in case you need it for work.

[alexanderruch]

caused a bug: #1318

[loosla]

caused a bug: #1318

👍 Fixed in v2.48.2