This is a Radicale 3 plugin to give users access based on a CalDav property RADICALE:acl.
It is supposed to be a comma separated list of the pattern user:rights, e.g.:
user1:rw, user2:r, user3:rw
To use this you will need a radicale web plugin which can set the RADICALE:acl property.
For example: https://github.com/sents/radicale-web-groups
The following configuration is needed:
[rights]
type = radicale-rights-acl