when using azapi_update_resource... wait for state change?

Hi,

Considering the following config:

```
data "azurerm_subscription" "current" {}

resource "azapi_update_resource" "EnableEncryptionAtHost" {
type = "Microsoft.Features/featureProviders/subscriptionFeatureRegistrations@2021-07-01"
resource_id = "/subscriptions/${data.azurerm_subscription.current.subscription_id}/providers/Microsoft.Features/featureProviders/Microsoft.Compute/subscriptionFeatureRegistrations/EncryptionAtHost"
body = jsonencode({
properties = {}
})
}
```

The problem is, the command runs but I can see that the resource is still in state "Registering"

`az feature show --namespace "Microsoft.Compute" --name "EncryptionAtHost"
{
"id": "/subscriptions/xxxxxxx/providers/Microsoft.Features/providers/Microsoft.Compute/features/EncryptionAtHost",
"name": "Microsoft.Compute/EncryptionAtHost",
"properties": {
"state": "Registering"
},
"type": "Microsoft.Features/providers/features"
}`

And the resource that depends on this feature to be enabled, throws an error saying the provider is not registered.

**The question is... Is there anyway to wait until the provider has been registered?**

Something like a null resource with a local-exec sleep command might do the trick:

```
resource "null_resource" "providers_registration_delay" {
provisioner "local-exec" {
command = "sleep 1500"
}
depends_on = [ azapi_update_resource.EnableEncryptionAtHostPreview,azapi_update_resource.EnableEncryptionAtHost ]
}

```

BUT, the problem is to include a 25 min delay (that's what it took!) that would then run on every execution...

... Maybe another API query that waits for state value or something? I've been checking the azapi provider documentation and I can't find a way to do something like this...

Any ideas?

Many thanks and best regards,

Start by reproducing the configuration with azapi_update_resource and checking the Azure CLI command `az feature show --namespace "Microsoft.Compute" --name "EncryptionAtHost"`. Investigate how the provider handles asynchronous Azure resource operations and determine where a state wait could belong; done means dependent resources apply successfully only after the feature reaches the registered state.

Written by the indexing model from the issue text.