Remove test suites

[morremeyer]

With in-memory SQLite databases used for testing, we can remove the test suites since each in-memory database is distinct.

This adds two lines of code to each test that needs the database (calling the setup function and then deferring the teardown), but this is a better developer experience than the test suites currently since these are not well integrated into IDEs.

[morremeyer]

When implementing this, check if we can use hooks to clean up more efficiently: https://medium.com/@jarifibrahim/using-gorm-hooks-to-clean-up-test-fixtures-in-golang-99b0fcb04354, probably in a combination with a TestMain function.

[morremeyer]

There has been movement in fixing the VSCode Go Extension to also support testify Suites again, see golang/vscode-go#3128.

If that gets released, this issue is obsolete.