feat: Add route to 0.0.0.0/0 & ::/0 (when IPv6 is enabled) on all public route tables (#1100)

* Fix logic for adding default route on public route tables

* Apply suggestions from code review

---------

Co-authored-by: Bryant Biggs <[email protected]>

Author: abohne

main.tf

@@ -153,9 +153,9 @@ resource "aws_route_table_association" "public" {
 }
 
 resource "aws_route" "public_internet_gateway" {
-  count = local.create_public_subnets && var.create_igw ? 1 : 0
+  count = local.create_public_subnets && var.create_igw ? local.num_public_route_tables : 0
 
-  route_table_id         = aws_route_table.public[0].id
+  route_table_id         = aws_route_table.public[count.index].id
   destination_cidr_block = "0.0.0.0/0"
   gateway_id             = aws_internet_gateway.this[0].id
 
@@ -165,9 +165,9 @@ resource "aws_route" "public_internet_gateway" {
 }
 
 resource "aws_route" "public_internet_gateway_ipv6" {
-  count = local.create_public_subnets && var.create_igw && var.enable_ipv6 ? 1 : 0
+  count = local.create_public_subnets && var.create_igw && var.enable_ipv6 ? local.num_public_route_tables : 0
 
-  route_table_id              = aws_route_table.public[0].id
+  route_table_id              = aws_route_table.public[count.index].id
   destination_ipv6_cidr_block = "::/0"
   gateway_id                  = aws_internet_gateway.this[0].id
 }