6.0.0: Add support for multiple target groups

BREAKING CHANGES:

• The variable lb_arn is no longer used as it was made redundant in a previous release.
• target_group_name variable has been replaced with target_groups.
• The module now requires you to define the name of the target group(s) in the form of:

target_groups = [
  {
    target_group_name = "example"
    container_port = 80
  }
]

• A list of target_group_arns needs to be referenced with an index number. Example:

  load_balancer_arn = module.alb.arn
  port              = "80"
  protocol          = "HTTP"

  default_action {
    type = "forward"
    
    # Version 5.1.0 - previous
    target_group_arn = module.fargate.target_group_arn
    
    # Version 6.0.0 - current
    target_group_arn = module.fargate.target_group_arn[0]
  }
}

• ECS Service resources will be replaced to replace the load_balancer attribute.
• target_group resources will be destroyed and recreated.

ENHANCEMENTS:

• Added a new example to demonstrate the setup of multiple target groups.
• Utilise default VPC and subnet resources in examples.

MIGRATION PROCEDURE:

In your terraform code follow the above changes that need to be made. In the UI, these steps need to be taken:

1. Delete any listener rules associated with a target group created by this module.
2. Delete the target groups

Once done, run your terraform plan and apply to have a clean migration.

What you will see in your terraform plan and apply are the following:

1. Target groups and listener rules being recreated
2. ECS Services being destroyed and then recreated