Need the ability to add virtual private gateway as route option in aws::route-table.

[ianp94]

Dealing with a cluster with custom cidr routing using virtual private gateways. I would like to add a log of cidr addresses to set up custom routes in routes.gyro to keep gyro from attempting to delete these routes when performing gyro up.

Example of cidr addresses I'm attempting to add.

= Keep aws::route-table private-us-xxxx-1 (rtf-1234567)
    + Create route 0.0.0.0/0 to nat-12345
      · destination-cidr-block: '0.0.0.0/0'
      · nat-gateway: aws::nat-gateway us-east-1a
    - Delete route x.x.x.x/x to virt-gateway-012343215
    - Delete route x.x.x.x/x to virt-gateway-012343215
    ...
    ...

Current gyro structure inside of routes.gyro using transit-gateway:

client-route-cidrs: ["x.x.x.x/x",
    "x.x.x.x/x"]
    
@for client-cidr -in $client-route-cidrs
            route
                destination-cidr-block: "$(client-cidr)"
                transit-gateway: 'virt-gateway-012343215'
            end
@end

when using transit gateway, I get the following error when performing gyro up:

Caused by: Error: Can't set route to [{destination-cidr-block=0.0.0.0/0, nat-gateway=aws::nat-gateway us-xxxx-1}, {destination-cidr-block=x.x.x.x/x, transit-gateway='virt-gateway-012343215'}, {destination-cidr-block=x.x.x.x/x, transit-gateway='virt-gateway-012343215'}] because it can't be converted to an instance of java.util.Set<gyro.aws.ec2.RouteResource>!