Allow different LB listener port and target port

[JohnPreston]

In some cases, it might be useful for development perspective to have a load balancer listen on one port and sent traffic to the microservice on a different one.

In the local environment, people for ports would because of ports opening do

serviceA:
  ports:
    - 8080:80
    - 8081:443

serviceB:
  ports:
    - 8180:80
    - 8181:443

that way both service A and B are exposed to the user and do not have overlapping ports.

Similarly, if a micro-service has a port defined with <port>:<port> and uses a load-balancer then the load-balancer should have a listener using the first port to target the microservice, and the second port used as the exposed port of the microservice.

[JohnPreston]

See https://nightly.docs.ecs-composex.lambda-my-aws.io/modules_syntax.html#acm-syntax-reference