[SE-4485] Discovery: workflows / timeline / sequence of actions

• Define user workflows (refunds, worklogs, regeneration, payments, onboarding, offboarding, dates, …)
• Including special workflows (e.g. held payments) though they can be improved later
• Think about how everything combines together
• Create a diagram or a document as a reference for the implementation tasks

TODO: use task template

Idea (to be confirmed): In sprint 248, timeboxed to a small amount (4 h. TBD), and just to start the base so that Fixate can continue it.