Add azurerm_firewall management IP configuration

[draggeta]

This PR adds the management IP configuration for the Azure Firewall. This allows for forced tunneling to be configured by configuring a UDR on the AzureFirewallSubnet.

To do:

• update read function
• update create function
• update delete function
• clean up code
• update tests
• update docs

Closes #7152

Acceptance test

❯  go test -timeout 180m -v -ldflags="-X=github.com/terraform-providers/terraform-provider-azurerm/version.ProviderVersion=acc" `
>> github.com\terraform-providers\terraform-provider-azurerm\azurerm\internal\services\network\tests `
>> -run "^TestAccAzureRMFirewall_withManagementIp" -count=1

=== RUN   TestAccAzureRMFirewall_withManagementIp
=== PAUSE TestAccAzureRMFirewall_withManagementIp
=== CONT  TestAccAzureRMFirewall_withManagementIp
--- PASS: TestAccAzureRMFirewall_withManagementIp (793.90s)
PASS
ok      github.com/terraform-providers/terraform-provider-azurerm/azurerm/internal/services/network/tests                                                       796.110s

[tombuildsstuff]

hey @caius

Thanks for this PR :)

Taking a look through this is off to a good start - if we can fix up the comments left inline (and the tests pass) then this otherwise LGTM 👍

Thanks!

[draggeta]

I'm still not sure about the wording. You can change the management_ip_configuration block without recreating the firewall. It only forces a new resource when you change the subnet_id. Adding or removing the block does force a new resource of course.

[manicminer]

@dragetta I think you pretty much got it there! How about:

Suggested change

	* `management_ip_configuration` - (Optional) A `management_ip_configuration` block as documented below, which allows force-tunnelling of traffic to be performed by the firewall. Changing this forces a new resource to be created.
	* `management_ip_configuration` - (Optional) A `management_ip_configuration` block as documented below, which allows force-tunnelling of traffic to be performed by the firewall. You can add and remove this block, however changing `subnet_id` in an existing block forces a new resource to be created.

[draggeta]

@manicminer I've adjusted your wording a bit. Let me know if this is ok.

[manicminer]

@draggeta briiliant 👍

[manicminer]

Test results:

[ghost]

This has been released in version 2.28.0 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 = "~> 2.28.0"
}
# ... other configuration ...

[ghost]

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