New resource azurerm_ip_group_cidr

[tiwood]

This adds a new resource that allows us to manage the CIDRs/IPs in an existing IP Group

Example Usage

resource "azurerm_resource_group" "example" {
  name     = "test-rg"
  location = "West Europe"
}

resource "azurerm_ip_group" "example" {
  name                = "test-ipgroup"
  location            = azurerm_resource_group.test.location
  resource_group_name = azurerm_resource_group.test.name
}

resource "azurerm_ip_group_cidr" "example" {
  ip_group_id = azurerm_ip_group.example.id
  cidr        = "10.10.10.0/24"
}

[tiwood]

@katbyte @tombuildsstuff
can some1 take a look?

We need a way to add/remove from CIDR groups programmatically and might need to use a custom built provider if its unclear if this gets merged into the official provider.

[tombuildsstuff]

hey @tiwood

Thanks for this PR - apologies for the delayed review here.

I've taken a look through and whilst on the whole this is looking pretty good, we're going to need to fix the azurerm_ip_group resource such that we don't introduce a breaking change to users configurations here - I've left some notes inline about this.

However if we can fix this up then we should be able to take another look 👍

Thanks!

[tombuildsstuff]

unfortunately this'd be a breaking configuration change, instead we'll need to revert this:

Suggested change

	ConfigMode: pluginsdk.SchemaConfigModeAttr,
	Optional: true,
	Computed: true,
	Optional: true,

and instead split the Create and Update methods here such that we retrieve the existing value for cidrs from the API and reuse this during the update, unless the cidrs block has changed, for example:

existing, err := client.Get(...)
if err != nil { .. }

update.Properties.Cidrs = existing.Properties.Cidrs
if d.HasChange("cidrs") {
    update.Properties.Cidrs = expandCidrs(d.Get("cidrs").([]interface{})
}

which'd allow users to make use of ignore_changes to ignore changes to the cidrs block on this resource, and use the separate resource instead - which'd need to be called out in the documentation for both of these resources

[katbyte]

Superseded by #17321

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