Feature/ram share multiple principals

[paulrob-100]

what

• allow transit gateway to be shared with multiple AWS Organization OUs or accounts
• Replaces variable ram_pricipal with ram_pricipals which is a list

why

• Useful in the multi-account example when you don't want to share with the entire Organization and there are multiple OUs/Accounts that will need to attach their local account vpcs to the tgw
• Fixes bug with the try function in principal attribute which always results in the empty string when var.ram_principal has a value - in that case data.aws_organizations_organization.default[0] doesn't exist

references

• Clarify the multi-account example a little
• Rebased onto #13

[mergify[bot]]

This pull request is now in conflict. Could you fix it @paulrob-100? 🙏

[nitrocode]

@paulrob-100 could you remove the changes unrelated to the multiple principals ?

I think we can do something as simple as this

locals {
  enabled = module.this.enabled

  ram_resource_share_enabled = local.enabled && var.ram_resource_share_enabled

  ram_principals = toset(concat(var.ram_principals, data.aws_organizations_organization.default.*.arn))
}

resource "aws_ram_principal_association" "default" {
  for_each = local.ram_resource_share_enabled ? toset(local.ram_principals) : toset([])

  principal          = each.value
  resource_share_arn = try(aws_ram_resource_share.default[0].id, "")
}

Also @paulrob-100 so you're unblocked, we're also outputting the ram_resource_share_id so principals can be attached to the RAM share from outside the module.