printer_state_message is not mandatory
Merge pull request #89 from ticosax/samll-fix

printer_state_message is not mandatory
Simplify argument passing by moving operation_attributes out of header
Extend Print-Job with a sub operation GROUP job-attributes-tag
styling and typo
Create-Job-Subscription does not seem implemented on CUPS

And the RFC contradict the CUPS documentation. So its hard to implement
something right
Weird
Merge pull request #90 from ticosax/extend-print-job

Extend print job
Mention CUPS ticket in docstring to explain why it is not usable