Feature Request: Multi-line label value with nested blocks

[polarathene]

See these references:

• Add a converter #749 (comment)
• How do I create Docker labels for caddy-l4? #702 (comment)
• Layer4 label not recognized after build #765 (comment)
• Ability to escape periods from CDP parsing in labels #767 (comment)

There's a variety of issues beyond those where users would benefit from this feature.

• It also would remove the workaround I suggest above which requires individual snippets to be mounted into the CDP container for import, as the equivalent could be defined as a label for importing if necessary.
• For configuration that is one-off for a container, the config would be much more easier to read and solve the problem of CDP not having working support for config scenarios in the references above.

3 examples if the feature existed

services:
  supabase-db:
    labels:
      # Far more pleasant than what the user attempted across multiple labels (and failed):
      # https://github.com/lucaslorentz/caddy-docker-proxy/issues/765#issuecomment-3691818216
      # https://github.com/lucaslorentz/caddy-docker-proxy/issues/702#issuecomment-2765241269
      'caddy.layer4.:5432': |
        @postgres tls sni supabasedb.example.com
        route @postgres {
          tls {
            connection_policy {
              alpn postgresql
          }
          proxy {{upstreams 5432}}
        }

services:
  example:
    labels:
      caddy: example.localhost
      # Importing a snippet from a custom Caddyfile base to use import "blocks" args:
      # https://github.com/lucaslorentz/caddy-docker-proxy/issues/767#issuecomment-3691842054
      # https://caddyserver.com/docs/caddyfile/directives/import#syntax
      'caddy.import': |
        import extendable-proxy {
          proxy_target {
            to 10.0.0.1
          }
          proxy_options {
            transport http {
              tls
            }
          }
        }

---

# Connect all services in other Compose configs to CDP via this network:
networks:
  default:
    name: caddy-net

services:
  reverse-proxy:
    image: lucaslorentz/caddy-docker-proxy:2.10
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    # Compose V2 does not require quotes for ports (no longer mistaken as hexadecimal).
    # `443/udp` for HTTP/3 support:
    ports: [80:80/tcp, 443:443/tcp, 443:443/udp]
    # Applying a global config via label with full block config:
    # https://github.com/lucaslorentz/caddy-docker-proxy/issues/695#issuecomment-2741982290
    labels:
      caddy: |
        dynamic_dns {
          # Use the `file` placeholder for secrets instead of `env`,
          # this is a more secure practice that has reduced risk of unintentional exposure:
          provider cloudflare {file./path/to/CLOUDFLARE_API_TOKEN}
          domains {
            # Use `env` placeholder for dynamic data:
            {env.DOMAIN}
          }
          check_interval 5m
          versions ipv4
        }

Without the feature proposed, one can configure the equivalent via a custom Caddyfile which looks like this if using the inline Docker Compose configs feature (or alternatively using an import directive via label + separate config workaround should work too):

services:
  reverse-proxy:
    # Providing your own base `Caddyfile` requires this ENV:
    environment:
      CADDY_DOCKER_CADDYFILE_PATH: /etc/caddy/Caddyfile
    configs:
      - source: caddy-config
        target: /etc/caddy/Caddyfile

configs:
  caddy-config:
    content: |
      # Global Settings
      { ... }

      # Anything else you'd like in your base `Caddyfile` after global settings goes here

---

Presumably if the label value is multi-line, that would be sufficient to toggle the parser logic to support this functionality? Insert the config value at the label key for the generated Caddyfile?