add groups section in the getting started guide.
Suggest to prefer configuration with env vars instead of modifying
the default configuration file
Signed-off-by: Nicola Murino <nicola.murino@gmail.com>
This makes it easier to set environment variables on some operating systems.
Setting configuration options from environment variables is recommended if
you want to avoid the time-consuming task of merging your changes with the
default configuration file after upgrading SFTPGo
Signed-off-by: Nicola Murino <nicola.murino@gmail.com>
