I am guessing the owner, developer and lead should be employees. In that case you can set associations from the project to the employee, i.e one for owner, one for the lead.
If there is only one owner(employee) you make the association *-1 from project to employee.
If it is possible to have more developers(employees) you make the assocation *-*
See https://docs.mendix.com/refguide/associations and https://gettingstarted.mendixcloud.com/