add ability to emit a lock file

the coursier CLI has a resolve option and -t but the output is more useful for humans than tools.

Would you be open to a PR to add the ability to emit a JSON lock file?

I imagine it would list all the constraints that went in (all the artifacts + versions), and then list the minDependencies optionally including sha256 hashes of all the artifacts.

This is suitable for checking into a version control for a fully reproducible description of the classpath used to build.

This protects people from mutable changes in repositories (which are possible) causing hard to diagnose issues (not noticing that the resolution changed).

If this sounds like it would be useful, I can see about sending some PRs to implement this.

[aucampia]

Actually fetch, launch, bootstrap and install should also be able to operate with a lockfile

[aucampia]

I think what would be quite ideal is if resolve was able to emit json - similar to cs fetch --json-output-file ... - and then for cs fetch to be able to use that, so for example:

cs resolve org.codehaus.groovy:groovy-all:3.0+ --json-output-file /var/tmp/coursier-lock.json
cs fetch --json-input-file /var/tmp/coursier-lock.json