- backport >=py38 Literal type
- update configuration sample
- add missing config filepath to systemd service
- make config sections optional
BREAKING CHANGE: the playout config schema has been changed like the following:
- the top section 'pypo' was renamed to 'playout'
- the 'playout.ls_*' entries were renamed to 'playout.liquidsoap_*'
- the 'playout.*_dir' entries were removed
- the 'playout.api_client' entry was removed
- the 'playout.record_file_type' entry was renamed to 'playout.record_file_format'
- the 'playout.base_recorded_files' entry was removed
- the 'playout.poll_interval' entry was removed
- the 'playout.push_interval' entry was removed
- the 'playout.cue_style' entry was removed
- use working dir for storing files
BREAKING CHANGE: the playout working directory changed from '/var/tmp/airtime/pypo/' to '/var/lib/libretime/playout' when running with systemd and the current directory by default.