Fix validation in resource azurerm_virtual_network_gateway for zone-redundant VPN gateways

[dominik-lekse]

Description

This pull request fixes an issue with the azurerm_virtual_network_gateway in which the validation prevents from creating zone-redundant VPN virtual network gateways.

• In add VpnGW skus #3171, zone-redundant gateway types have been added effectively for ExpressRoute gateway but not yet for VPN gateways.
• I have cleaned up the validation for the sku attribute to rely on the "sub validators" to avoid ambiguity.

New or Affected Resource(s)

• azurerm_virtual_network_gateway

References

• Fixes Could not use VpnGw1AZ, VpnGw2AZ, and VpnGw3AZ SKU's with resource azurerm_virtual_network_gateway #3314
• add VpnGW skus #3171

[katbyte]

Good idea @dominik-lekse! Thanks for this 👍

[ghost]

This has been released in version 1.28.0 of the provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading. As an example:

provider "azurerm" {
	version = "~> 1.28.0"
}
# ... other configuration ...

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. If you feel I made an error 🤖 🙉 , please reach out to my human friends 👉 hashibot-feedback@hashicorp.com. Thanks!