* Single `<D:propstat>` element in PROPPATCH response
* Allow multiple `<D:set>` and `<D:remove>` elements
* Improve log messages
* Fix date filter
* Improve sanitization of collection properties
* Cancel mkcalendar request on error
* Use **renameat2** on Linux for atomic overwriting of collections
* Command Line Parser
* Disallow abbreviated arguments
* Support backend specific options and HTTP headers
* Optional argument for boolean options
* Load no config file for `--config` without argument
* Allow float for server->timeout setting
* Fix **is-not-defined** filter in **addressbook-query** report
* Add python type hints
* Add **multifilesystem_nolock** storage
* Add support for Python 3.9 and 3.10
* Drop support for Python 3.5
* Fix compatibility with Evolution (Exceptions from recurrence rules)