muster release v5.38.0

The CLI sign-in can print the URL instead of opening a browser, and honors $BROWSER. A sign-in always launched the platform opener (xdg-open, open, start) and printed the URL only when the opener failed, so a session driving its own browser never saw the URL. --no-browser on the login command, or MUSTER_NO_BROWSER=1 for every command that signs in, starts no browser process: the authorization URL goes to stdout and the CLI keeps waiting for the callback until the URL is opened elsewhere on the machine. Otherwise the commands in $BROWSER are tried before the platform default. (#1425)