Ensure storage_ip_rules regexall only matches /31 and /32, but leaves /30 alone since it is valid

[blongv]

Fixes #19

Based on https://learn.microsoft.com/en-us/azure/storage/common/storage-network-security?tabs=azure-portal#restrictions-for-ip-network-rules and my testing, /30 CIDRs should be allowed and are configurable as storage account firewall rules.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Changes proposed in this pull request

• Change regexall("/3.", cidr) to regexall("/3(1|2)", cidr) to ensure /30 CIDRs are passed through correctly.

If I have a data service tag resource as follows:

# az network list-service-tags --location usgovvirginia
#
data "azurerm_network_service_tags" "frontdoor" {
  location = var.azure_location
  service  = "AzureFrontDoor"
}

And I try configuring this module as follows:

  allowed_cidrs = concat(
    ["64.102.0.0/16"],
    data.azurerm_network_service_tags.frontdoor.ipv4_cidrs
  )

It will fail to apply the /30 CIDRs from Azure service tags to the storage account. For example, 20.140.152.52/30 will be changed to 20.140.152.52 and this means 20.140.152.53, 20.140.152.54, 20.140.152.55 will be blocked when they should be allowed.

@claranet/fr-azure-reviewers

[BzSpi]

Nice catch ! Thanks.