This PR refactor and clean up some parts of the template:

• upstream_name was set in$globals.vhosts two times, in the VIRTUAL_HOST and VIRTUAL_HOST_MULTIPORTS loops. It's been deduplicated to the third loop over $globals.vhosts.
• hard to read expressions like when (hasKey $fooDict $bar) (get $fooDict $bar) "defaultValue" has been replaced with the slightly clearer get $fooDict $bar | default "defaultValue".
• removal / simplification of the excess logic revolving around setting the port to legacy for containers using VIRTUAL_HOST.

and fix a few things on the debug endpoint:

• addition of a terminal \n character to the response so that curl | jq on the endpoint work correctly.
• when a given path + port had more than one container, the whole RuntimeContainer struct of the additional containers where incorrectly kept, resulting in the paths being stripped from the response.

Due to the aforementioned removal of the legacy port logic, this configuration:

services:
  # ...

  app1:
    image: nginx
    environment:
      VIRTUAL_HOST: nginx-proxy.tld
      VIRTUAL_PORT: 8077
  
  app2:
    image: nginx
    environment:
      VIRTUAL_HOST: nginx-proxy.tld
      VIRTUAL_PORT: 8077
  
  app3:
    image: nginx
    environment:
      VIRTUAL_HOST_MULTIPORTS: |-
        nginx-proxy.tld:
          "/":
            port: 8077

Now result in this in the vhost.paths section of the debug endpoint response:

{
   "/":{
      "dest":"",
      "keepalive":"auto",
      "network_tag":"external",
      "ports":{
         "8077":[
            {
               "Name":"compose-app2-1"
            },
            {
               "Name":"compose-app1-1"
            },
            {
               "Name":"compose-app3-1"
            }
         ]
      },
      "proto":"http",
      "upstream":"nginx-proxy.tld"
   }
}

instead of this previously:

{
   "/":{
      "dest":"",
      "keepalive":"auto",
      "network_tag":"external",
      "ports":{
         "8077":[
            {
               "Name":"compose-app3-1"
            }
         ],
         "legacy":[
            {
               "Name":"compose-app2-1"
            },
            {
               "Name":"compose-app1-1"
            }
         ]
      },
      "proto":"http",
      "upstream":"nginx-proxy.tld"
   }
}

The resulting nginx configuration is inchanged.