Allow bringing your own alb listener

[izaaklauer]

Merge after #4444

Prior to this, our docs claimed we allowed users to bring their own alb listeners: https://developer.hashicorp.com/waypoint/plugins/aws-ecs#alb-listener_arn

But in practice, they would get this error:

$ waypoint deploy

» Deploying hello-app...
✓ Running deploy v22
✓ Deployment resources created
✓ Discovered service subnets
✓ Discovered alb subnets
✓ Using external security group hello-app-inbound
✓ Using internal security group hello-app-inbound-internal
✓ Using existing log group waypoint-logs
✓ Using existing execution IAM role "ecr-hello-app"
✓ Registered Task definition: waypoint-hello-app
✓ Using existing ECS cluster waypoint
✓ Created target group hello-app-01GQNGJSKZ557FNN7JPG7
✓ Modified ALB Listener to introduce target group
✓ Created ECS Service hello-app-01GQNGJSKZ557FNN7JPG7

» Performing operation locally
✓ Finished building report for ecs deployment
✓ Determining status of ecs service hello-app-01GQNGJSKZ557FNN7JPG7
✓ Found existing ECS cluster: waypoint
⚠️ 1 cluster READY, 1 service READY, 1 task MISSING
⚠️ Waypoint detected that the current deployment is not ready, however your application
might be available or still starting up.

» Releasing...

» Performing operation locally
✓ Running release v17
! ValidationError: A load balancer ARN must be specified
        status code: 400, request id: f6328bdb-0616-484e-8654-140b8c2c1ca9

Waypoint hcl contents:

project = "hello-app"

app "hello-app" {
  build {
    use "pack" {}
    registry {
      use "aws-ecr" {
        region     = "us-east-1"
        repository = "waypoint-example"
        tag        = "latest"
      }
    }
  }

  deploy {
    use "aws-ecs" {
      region = "us-east-1"
      memory = "512"
      alb {
        listener_arn = "arn:aws:elasticloadbalancing:us-east-1:863953081260:listener/app/waypoint-ecs-hello-app/3cdb806e2340b21e/1c2034ee6148da78"
        subnets      = ["subnet-0bd08267365065f8e","subnet-04ff6753f3ba35e49","subnet-02c9aaa7732de7eb7","subnet-047d5841370712b24","subnet-086d533750a535ea5","subnet-0f8dd2e1826266538"]
      }

    }
  }
}

This change brings us in line with our docs.

[izaaklauer]

This looks like it could be a breaking protobuf change, but I don't think it is! It's not changing field numbers. I also tried releasing a deployment made with the previous compiled protobufs, and it worked.

[izaaklauer]

Here's the bug. If you specify your own target group arn, target.LoadBalancerArn would be an empty string, and you'd get a 400 on this call.

[izaaklauer]

In the existing logic, a user could specify a listener arn in the platform config, but we weren't making that available to the releaser.

[izaaklauer]

Converted this back to a draft for now - thinking about modifying it to take an alb arn as input instead of a listener arn. Waypoint should probably always "own" the alb listener, as it's going to need to modify it for every deployment.

[izaaklauer]

The problem here is that if someone wants to manage their ALB through terraform, they need to have terraform create the alb listener, and give that to waypoint. But if terraform creates the listener, it also needs to create the listener's default rule (which waypoint needs to modify). So every time you run the terraform after wayoint modifies the listener, terraform modifies it back the the default state, and the app loses traffic!

Replacing this pr with #4457