[Enhancement]: IPAM subnet reservations

[drewmullen]

Description

AWS Announced VPC Subnets can get their CIDR from AWS IPAM IP Reservations. I'm not 100% what the implementation will look like but will update this issue as the service features become available publicly.

Based on the blog I believe the following changes need to be made

1. aws_vpc_ipam_pool needs to be able to set resource planning to a vpc
2. aws_subnet needs to specify the cidr block is from an ipam pool id, ip netmask

These values are

• CreateSubnet: Ipv4IpamPoolId, Ipv4NetmaskLength, Ipv6IpamPoolId, Ipv6NetmaskLength
• CreateIpamPool - SourceResource which is a new nested type: https://github.com/aws/aws-sdk-go-v2/blob/main/service/ec2/types/types.go#L7919

Affected Resource(s) and/or Data Source(s)

• aws_vpc_ipam_pool
• aws_subnet

Potential Terraform Configuration

### ipam pool

resource aws_vpc_ipam_pool main {
  source_resource {

    resource_id = <>

    resource_owner = <> # account owner id

    resource_region = <>

    // The source resource type.
    ResourceType = "vpc" # https://github.com/aws/aws-sdk-go-v2/blob/main/service/ec2/types/enums.go#L4776

  }
}

### vpc subnet

```hcl
resource aws_subnet main {
  ipv4_ipam_pool_id = ""
  ipv6_ipam_pool_id = ""

  ipv4_netmask_length = #
  ipv6_netmask_length = #
}

### References

_No response_

### Would you like to implement a fix?

None

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[drewmullen]

To confirm design I need to try this out with CLI commands. The docs arent updated yet because #reinvent

[laminarcode]

API documentation now available: https://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_CreateSubnet.html Kindly implement the following attributes in terraform:

• Ipv4IpamPoolId
• Ipv4NetmaskLength
• Ipv6IpamPoolId
• Ipv6NetmaskLength