Add the buildarr compose command

[Callum027]

This PR adds a new buildarr compose CLI command for generating Docker Compose files from Buildarr configurations, and log the contents of the file to standard output.

The file itself is very basic and will probably require adjustment from the user to get it to work the way they want, but the Docker Compose file will have the following:

• Image tags matching the version defined in the Buildarr configuration file
• Restart policy set on all services
• Any required volumes created
• Service dependencies added based on instance-to-instance links present in the Buildarr configuration
• Buildarr itself added as a service in daemon mode, to deploy instance configurations and keep them up to date

To save the contents to the file, simply run:

buildarr compose /opt/buildarr/buildarr.yml > /opt/buildarr/docker-compose.yml

Example buildarr.yml:

---
sonarr:
  instances:
    sonarr-hd: {}
    sonarr-4k:
      settings:
        media_management:
          root_folders:
            - /tmp/videos
        profiles:
          language_profiles:
            definitions:
              English:
                languages:
                  - "English"
        import_lists:
          definitions:
            "Sonarr (HD)":
              type: "sonarr"
              root_folder: "/tmp/videos"
              quality_profile: "Any"
              language_profile: "English"
              full_url: "http://sonarr-hd:8989"
              instance_name: "sonarr-hd"

Output docker-compose.yml:

---
version: '3.7'
services:
  sonarr_sonarr-hd:
    image: lscr.io/linuxserver/sonarr:latest
    volumes:
      sonarr_sonarr-hd: /config
    hostname: sonarr-hd
    restart: always
  sonarr_sonarr-4k:
    image: lscr.io/linuxserver/sonarr:latest
    volumes:
      sonarr_sonarr-4k: /config
    hostname: sonarr-4k
    restart: always
    depends_on:
    - sonarr_sonarr-hd
  buildarr:
    image: callum027/buildarr:0.4.0
    command:
    - daemon
    - /config/buildarr.yml
    volumes:
    - type: bind
      source: /opt/buildarr
      target: /config
    restart: always
    depends_on:
    - sonarr_sonarr-hd
    - sonarr_sonarr-4k
volumes:
- sonarr_sonarr-4k
- sonarr_sonarr-hd