Expand API test coverage

It would be good if every entity was mentioned within `test_multiple_paths.py`.
The tests in thie file should not actually be executed for every entity, but
when not, a reason should be noted.

Slightly expand test coverage by adding ActivationKey and User entities to each
test.
This may be a bug. Shouldn't permission to interact with a given API endpoint be flat-out denied if the user does not provide any credentials?