test_client: Migrate nominal collection scenario to use requests_mock_datadir
Motivation: I want to understand tests without reading through the mocks... I also want to improve the coverage in there because !101 (closed) diff showed it's missing a lot.
full disclosure, I don't trust nor like much that part of the code, so i'm trying to give it some love nonetheless.
... Prior to actually open the new swhid parameter in the cli.
Test Plan
tox
Migrated from D4204 (view on Phabricator)