feat: better output and exit code from incomplete commands

[infinitewarp]

This changes the way argparse validates incomplete subparser (subcommand) inputs. By setting required=true, argparse correctly halts processing, displays a useful error message, and returns a non-zero exit code.

Old handling of incomplete commands:

$ qpc server
usage: qpc [-h] [--version] [-v] {server,cred,source,scan,report,insights} ...

positional arguments:
  {server,cred,source,scan,report,insights}

options:
  -h, --help            show this help message and exit
  --version             show program's version number and exit
  -v                    Verbose mode. Use up to -vvvv for more verbosity.

$ echo $?
0

Note that the old output simply dumps the top-level help message which does not actually help with the provided server subcommand, and it exits with 0 which wrongly indicates success.

New handling of incomplete commands:

$ qpc server
usage: qpc server [-h] {config,login,logout,status} ...
qpc server: error: the following arguments are required: action

$ echo $?
2

[abellotti]

this looks great @infinitewarp, nice and surgical. Are there any doc updates needed somewhere where we show the old usage/responses ?