Peer VPCs across AWS Accounts and Regions

[Eric Thompson (ethompsy)]

what

• Split the module between two AWS provider aliases: aws.requestor and aws.acceptor

why

• This allows peering connections across AWS account and/or regions
• The same provider can be passed into both arguments to achieve peering within the same AWS account and region

references

Terraform Documentation on Provider Usage:

https://developer.hashicorp.com/terraform/language/modules/develop/providers#:~:text=Provider%20configurations%20can%20be%20defined%20only%20in%20a%20root%20Terraform%20module.

TL;DR: "Provider configurations can be defined only in a root Terraform module."

Deprecates: https://github.com/cloudposse/terraform-aws-vpc-peering-multi-account

-closes #52
-closes #42

[atatevyan]

Thanks for this PR. Indeed, there is no point of maintaining two very similar modules for the same purpose.

And I suggest, this module is adjusted to be compatible with the https://github.com/cloudposse/terraform-aws-vpc-peering-multi-account, so that we don't break things when migrating to the one unified module in the future.

[atatevyan]

Consider using aws_vpc_peering_connection_options resource instead.

[atatevyan]

Typically, this one won't be needed for the same account/same region case, as it will be treated as the same resource as requester by AWS. For this very reason, the multi-account module exhibits incorrect behavior, trying to rewrite requester tags with accepter tags and vice versa with every next plan/apply cycle, never reaching state convergence. Here, you're using same tags for both requester and accepter, so shouldn't be an issue, however this will break compatibility with multi-account module, if someone tries to migrate from it to this reworked module.