setting up CDK context values to make stack synth more deterministic rather than relying on runtime lookups

example.ts

// Given a pre-existing VPC network layout with stable ID, subnets, and routing tables
// this CDK setup code will populate the context necessary for lookups without going
// through synth and maintaining the context cache outside of version control

private setupFooVpcContext(): void {
  // this is the CDK context info for the Demo VPC in the example account
  const account = "1234"
  const region = "us-west-2"
  const tag = "MyDemoVPC"
  const contextKey =
      `vpc-provider:account=${account}:filter.tag:Name=${tag}:region=${region}:returnAsymmetricSubnets=true';
  const contextData = {
      vpcId: 'vpc-TODO',
      availabilityZones: [],
      subnetGroups: [
          {
              name: 'Public',
              type: 'Public',
              subnets: [
                  {
                      subnetId: 'subnet-TODO',
                      availabilityZone: 'us-west-2a',
                      routeTableId: 'rtb-TODO',
                  },
                  {
                      subnetId: 'subnet-TODO',
                      availabilityZone: 'us-west-2b',
                      routeTableId: 'rtb-TODO',
                  },
              ],
          },
      ],
  };

  this.node.setContext(contextKey, contextData);
}

// then you can use code like
const vpc = Vpc.fromLookup(this, 'AVPC', {
    vpcName: 'MyDemoVPC',
});