How to manage reservations?

Hi,

is there any way to to manage Reservations with `AzureRMR`?
I'm thinking about getting the list of Reservation Orders and then the list of all Reservations.

I was trying to get the resource with:
```
az <- get_azure_login()
az_resource$new(
token = az$token$credentials$access_token,
subscription = sub_id,
id = "/providers/microsoft.capacity/reservationOrders/{guid}/"
)
```

When I added the required `subscription` parameter I got this:

> Error: No API versions found
> In addition: Warning message:
> No stable API versions found, falling back to the latest preview version

That would be great to have a possibility to manage Reservations.
What I need now would be to only assign permissions for people/groups to the Reservation Orders.