Subcommands

[jentz]

• changes cli interface to use subcommands

This is the first step to bringing more structure to the CLI and breaking things down into sub commands and keeping the parsing of them separate we should have an easier time adding validation and tests.

References:

• https://eli.thegreenplace.net/2020/testing-flag-parsing-in-go-programs/
• https://www.janekbieser.dev/posts/cli-app-with-subcommands-in-go/