[RFE] support for defining default user groups during build time #106
Description
Current situation
Package maintainers are unable to set default user groups during build time.
Impact
Distros vary on what groups they assign to users by default. For example, Ubuntu, grants the groups: adm, audio, cdrom, dialout, dip, floppy, lxd, netdev, plugdev, sudo, and video. While Azure Linux grants the groups: wheel and sudo.
The recent Builder style API revisions have opened up the ability to define custom user groups when provisioning a user, via the .with_groups() method. However, the solution is not exposed at build time for distro maintainers to utilize this new feature.
Ideal future situation
During build time of azure-init, distro maintainers would be able to specify a list of default groups via build arguments or environment variables.
**Implementation options
Option 1)
Introduce a new env variable DEFAULT_USERADD_GROUPS, that is ingested by azure-init's main.rs and pass this value into a call to .with_groups() during provision(). If DEFAULT_USERADD_GROUPS is empty, continue to default to the singular group "wheel".
Option 2)
Introduce a new build argument to the cargo build command, that is ingested by azure-init's main.rs and pass this value into a call to .with_groups() during provision(). If the build argument is empty, continue to default to the singular group "wheel".