How to document project properties in gradle?

where to document/describe cross-cutting properties for gradle tasks?

example: a property named DB, which has a viable default but depending on its value tests are run against a specific database

so: gradle test -PDB=asd will run on ‘asd’ if the project has more test tasks for example test2 gradle test2 -PDB=asd will also run on ‘asd’

stackoverflow question, different - maybe easier to understand

workaround/etc: add an extra task named ‘advancedOptions’ and every plugin which adds properties which can be overridden drops a doLast() block into it