What does this do?

This is a radicale plugin to give users access to every principal collection matching the name of a OS group they are in. Group membership is taken from grp. The plugin simply checks if a user owns the calendar or is member of the group that owns the calendar and gives read and write permissions if the check is successful.

To actually discover collections that you have read access to, but don't own, you'll need something mirroring your readable collections in your own path.
For example: https://github.com/sents/radicale-share-collections

The following configuration is needed:

[rights]

type = radicale-rights-grp

# Optional; Strip a prefix from the OS groups.
group_prefix="loc"

This package also provides a command to create a canonical collection for a list of comma separated groups with radicale_create_groups.py /etc/radicale/config -g group1,group2,....