refactor: exclude path and uuid from ProjectSerializer
refactor: exclude path and uuid from ProjectSerializer

`fields` and `exclude` can't be used together, which introduced a mental block and the "readonly" fields solution.
But the doc says that `exclude` alone is exactly what we want: all fields minus the excluded ones

#4710: Improve project hierarchies

akvo/akvo-rsr,akvo/akvo-rsr,akvo/akvo-rsr,akvo/akvo-rsr