Add multi-container tasks to share namespaces within services

I am wondering if a tasks can be redefined as not only tied to one container but multiple, which are able to share namespaces (like Kubernetes PODS)?

This would allow for a proxy container (e.g. lyft/envoy, nginx) to do its magic like TLS termination,logging,tracing,... communicating via localhost to a service providing container service.

version: '4'
services:
  http:
    group:
     shared-namespaces: [network]
      components:
        web:
          # service only serving on 127.0.0.1
          image: nginx
        proxy:
          # service proxying 127.0.0.1:80 to 0.0.0.0:8080 
          image: envoy
          ports: [8080:8080]

Start by reviewing SwarmKit’s existing task, service, and scheduling model, then compare it with the Kubernetes Pod behavior described in the issue. Define how multiple containers would be grouped and which namespaces they could share; done requires an agreed design and implementation path for proxy and service containers communicating over localhost.