Pipeline steps and departments often correspond but not always. We have an animation department and also an animation pipeline step. There are separate pipeline steps for Roto and CU but these are done by the same department. There are some departments like production that have no corresponding pipeline step. We resource by department so I know that I have 1,500 person days of CU/Roto resourced on a certain job but we assign tasks by pipeline step so if I want to make a link between what we have resourced and how much work there is to be done I need to link departments and pipeline steps.
Thus I need to add a department field to the step entity