Is there a way to set an amount of time a member can work per day or on a project? The idea behind this is that OpenProjects than calculates the start or end date of a task. E.g a task takes 10h, the assigned member can work 4h/pay,  so the task takes 2 1/2 days to complete. 

This should avoid that too much (or too less) work is assigned to a member.