#3061 - Test for "Too many rental tokens are being created"

I've moved this live, but I still want Jan to make a test for this.

To make a test for this, checkout the broken version of this (commit:c335e63e63f7b2219e6edb5f600c1289fa7f124c). Then make a test that has a UiNodeRental fixture with no start_at or end_at. Then make a UiNodeLog RENTAL_START fixture that has alt_card_id with the id for the UiNodeRental fixture. Then the test will save the UiNodeLog and it should verify that the start_at for the UiNodeRental got set to the timestamp from the RENTAL_START. It's important to make sure that this works on the broken branch to verify that you've created the UiNodeLog and UiNodeRental fixtures correctly because we're going to be testing a negative result and so it's really easy to mess up the fixtures so that the rental doesn't get updated for some other reason.

Then switch to the master branch and change the test so that it uses exactly the same fixtures, but verifies that the UiNodeRental does NOT get updated when the UiNodeLog is saved.