cubicweb-medicalexp #3489098 ProcessingRun and execution graphs [open]

ProcessingRun's are chained using this relation:
followed_by = SubjectRelation('ProcessingRun' , cardinality='??', inlined=True)

This works fine with execution chains. However execution graphs might be more complex than a simple chain: parallel runs, etc.

Either the cardinality could be changed, or a ProcessingRunGraph entity added.

I hope we haven't missed the purpose of "followed_by"!

done in<not specified>
closed by<not specified>