do not force symmetrical definitions of services in cells

[drewmullen]

example of non-symmetrical defintions, deploying cell resources to a db cluster:

module "primary_app_us_east_1" {
  source = "../.."

  name                    = "${var.name}-primary"
  create_recovery_cluster = false
  create_recovery_group   = false

  cells_definition = {
    us-east-1a = {
      autoscaling          = module.sample_us_east_1.asg_arns["us-east-1a"]
      elasticloadbalancing = module.sample_us_east_1.lb_arns["us-east-1a"]
    }
    us-east-1b = {
      autoscaling          = module.sample_us_east_1.asg_arns["us-east-1b"]
      elasticloadbalancing = module.sample_us_east_1.lb_arns["us-east-1b"]
    }
    db-cluster = {
      rds = module.sample_us_east_1.db_cluster
    }
  }
}