NSX-T Edge Gateway automatic IP assignment

[Didainius]

Closes #743

This PR adds support for 2 new different IP allocation modes in addition to the already existing manual IP range allocation using subnet blocks. Sadly, it was not possible to make all settings available in a single subnet block, because of Terraform schema limitations which are not in control by provider developers. (the main problem with TypeSet blocks is that they would produce inconsistent plan for allocation ranges, when an allocated IP count is increased)

The new modes are:

• subnet_with_total_ip_count + total_allocated_ip_count -> automatic IP allocation in any of the defined subnets (up to total_allocated_ip_count)

resource "vcd_nsxt_edgegateway" "nsxt-edge" {
  org  = "cloud"
  vdc  = "nsxt-vdc-cloud"
  name = "edge"

  external_network_id = vcd_external_network_v2.ext-net-nsxt.id

  total_allocated_ip_count = 100
  subnet_with_total_ip_count {
    gateway       = tolist(vcd_external_network_v2.ext-net-nsxt.ip_scope)[0].gateway
    prefix_length = tolist(vcd_external_network_v2.ext-net-nsxt.ip_scope)[0].prefix_length
    primary_ip    = tolist(tolist(vcd_external_network_v2.ext-net-nsxt.ip_scope)[0].static_ip_pool)[0].start_address
  }

  subnet_with_total_ip_count {
    gateway       = tolist(vcd_external_network_v2.ext-net-nsxt.ip_scope)[1].gateway
    prefix_length = tolist(vcd_external_network_v2.ext-net-nsxt.ip_scope)[1].prefix_length
  }
}

Note. Due to API limitations, the behavior of this function is different when allocating IPs and when deallocating. When allocating - it is sufficient to just use QuickAddAllocatedIPCount field, while deallocation requires manual structure adjustment

• subnet_with_ip_count -> automatic IP allocation for a per subnet case

resource "vcd_nsxt_edgegateway" "nsxt-edge" {
  org  = "cloud"
  vdc  = "nsxt-vdc-cloud"
  name = "edge"

  external_network_id = vcd_external_network_v2.ext-net-nsxt.id

  subnet_with_ip_count {
    gateway       = tolist(vcd_external_network_v2.ext-net-nsxt.ip_scope)[0].gateway
    prefix_length = tolist(vcd_external_network_v2.ext-net-nsxt.ip_scope)[0].prefix_length

    primary_ip         = tolist(tolist(vcd_external_network_v2.ext-net-nsxt.ip_scope)[0].static_ip_pool)[0].end_address
    allocated_ip_count = "9"
  }

  subnet_with_ip_count {
    gateway            = tolist(vcd_external_network_v2.ext-net-nsxt.ip_scope)[1].gateway
    prefix_length      = tolist(vcd_external_network_v2.ext-net-nsxt.ip_scope)[1].prefix_length
    allocated_ip_count = "10"
  }
}

Additionally, this PR will add new attributes:

• used_ip_count - returns the number of IPs that are used by the services in this Edge Gateway
• unused_ip_count - returns the number of IPs that are allocated, but not yet used by any service in the Edge Gateway
• total_allocated_ip_count (must be used for subnet_with_total_ip_count however, it will return computed values in other cases as well)

Testing

• Acceptance tests with tags nsxt and gateway passed on 10.3.0, 10.4.0, 10.4.1.
• Binary tests with tag gateway passed on 10.4.1
• Upgrade tests with tag gateway passed on 10.4.1 (also added vcd.ResourceSchema-vcd_nsxt_edgegateway.tf to skip)

[adambarreiro]

First scan

[lvirbalas]

This PR slipped my attention, sorry... My main question is how could we clarify the auto_subnet vs. auto_allocated_subnet concepts (comment in-line).

[adezxc]

Thanks for this PR!