Improve unit-tests for API

I have cleaned up the API unit-tests such that the tests cleans up after themselves (so, delete the user+chart at the end of the test).

I've also added testing of the publish-functionality.

During the test, I found that it was impossible to delete a user, because the API will always receive the user-id as an string, but it is stored as an integer, so you would end up having `1 === '1'`, which failed.