feat: support score-compose init subcommand

[astromechza]

The init subcommand makes it easier to get started with Score compose!

$ score-compose init --help
The init subcommand will prepare the current directory for working with score-compose and prepare any local
files or configuration needed to be successful.

A directory named .score-compose will be created if it doesn't exist. This file stores local state and generally should
not be checked into source control. Add it to your .gitignore file if you use Git as version control.

The project name will be used as a Docker compose project name when the final compose files are written. This name
acts as a namespace when multiple score files and containers are used.

Usage:
  score-compose init [flags]

Examples:

  # Define a score file to generate
  score-compose init --file score2.yaml

  # Or override the docker compose project name
  score-compose init --project score-compose2

Flags:
  -f, --file string      The initial score file to ensure exists (default "./score.yaml")
  -h, --help             help for init
  -p, --project string   The name of the docker compose project

Global Flags:
      --quiet           Mute any logging output
  -v, --verbose count   Increase log verbosity and detail by specifying this flag one or more times

And when run:

$ score-compose ../cmd/score-compose/main.go init
INFO: Writing new state directory '.score-compose'
INFO: Initial Score file './score.yaml' does not exist - creating it
INFO: Read more about the Score specification at https://docs.score.dev/docs/

This dumps out a score file that looks like:

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• New chore (expected functionality to be implemented)

Checklist:

• My change requires a change to the documentation.
  • I have updated the documentation accordingly.
• I've signed off with an email address that matches the commit author.

[chrishumanitec]

In general, it is not considered good practice to check for a file before opening - rather favour attempting to open the file and then check the failure there. This is to avoid race conditions for file opening i.e. https://groups.google.com/g/golang-nuts/c/Ayx-BMNdMFo/m/4rL8FFHr8v4J

[astromechza]

Fixed up :) now just doing a direct read with error handling.

[chrishumanitec]

In general, it is not considered good practice to check for a file before opening - rather favour attempting to open the file and then check the failure there. This is to avoid race conditions for file opening i.e. https://groups.google.com/g/golang-nuts/c/Ayx-BMNdMFo/m/4rL8FFHr8v4J

In this case, using os.O_CREATE with os.O_EXCL will be an error if the file already exists.

[astromechza]

Fixed up :) now just doing a direct read with error handling and then a write if it doesn't exist.

[chrishumanitec]

LGTM