fix: Update routes when doing a vpc attachment

[velkovb]

Description

The VPC attachment block supports adding routes to an existing route table but that only works when you are creating a transit gateway. When you are just attaching a VPC to a shared gateway it doesn't work as it only looks at the Id of the internal resource.

Motivation and Context

This change would allow to update route tables when attaching VPCs to a shared transit gateway by taking parsing the tgw_id attribute as well. Logic is replicated from the aws_ec2_transit_gateway_vpc_attachment resource.

Breaking Changes

Not a breaking change.

How Has This Been Tested?

• I have updated at least one of the examples/* to demonstrate and validate my change(s).
• I have tested and validated these changes using one or more of the provided examples/* projects. It was tested with similar implementation to the multi-account setup.

• I have executed pre-commit run -a on my pull request

[github-actions]

This PR has been automatically marked as stale because it has been open 30 days
with no activity. Remove stale label or comment or this PR will be closed in 10 days

[velkovb]

can we remove the stale label?

[github-actions]

This PR has been automatically marked as stale because it has been open 30 days
with no activity. Remove stale label or comment or this PR will be closed in 10 days

[velkovb]

can we remove the stale label?

[obi-juan1971]

It would be great to have this fixed!!

[github-actions]

This PR has been automatically marked as stale because it has been open 30 days
with no activity. Remove stale label or comment or this PR will be closed in 10 days

[velkovb]

This is still valid

[bmurphey]

Not sure how much my approval means in the context of this community module, but this does look good to me and I've been using it successfully in my environment.

[mrobinson1022]

it would be super great if this PR could be merged, I tested it as well and it works flawlessly.

[velkovb]

I can't request review of the PR. @antonbabenko could you help?

[github-actions]

This PR has been automatically marked as stale because it has been open 30 days
with no activity. Remove stale label or comment or this PR will be closed in 10 days

[velkovb]

/remove-lifecycle stale

[bryantbiggs]

can you update/provide an example that demonstrates/validates this change?

[bryantbiggs]

and can we incorporate the changes in #102

[github-actions]

This PR has been automatically marked as stale because it has been open 30 days
with no activity. Remove stale label or comment or this PR will be closed in 10 days

[velkovb]

can you update/provide an example that demonstrates/validates this change?

I totally missed this. Yes, I will try to add an example.

[velkovb]

@bryantbiggs I think that actually the multi-account example covers this scenario. The problem is that here: https://github.com/terraform-aws-modules/terraform-aws-transit-gateway/blob/master/main.tf#L117 we only cover the case when the attachment is created when the tgw is created as well. When we just do an attachment with create=false we can't pass the tgw_id. My PR just fixes that and when you pass tgw_id on attachment it will take it into account.

Here is the example - https://github.com/velkovb/terraform-aws-transit-gateway/blob/fix/vpc-attachment-routes/examples/multi-account/main.tf#L98. I think it should be broken with current implementation.

[github-actions]

This PR has been automatically marked as stale because it has been open 30 days
with no activity. Remove stale label or comment or this PR will be closed in 10 days

[github-actions]

This PR was automatically closed because of stale in 10 days

[velkovb]

Can we re-open this PR?

[github-actions]

I'm going to lock this pull request because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues. If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.