Mitigate failed test cleanups by logging in if the user already exists

[jmoggr]

Closes #395

This does cause the following test to sometimes fail:

    const defaultProfile = unwrap(await rpc.get_active_user_profile.query());
    test.sequential("should get empty profile after user creation", () => {
        assert.strictEqual(defaultProfile.username, null);
        assert.strictEqual(defaultProfile.displayName, null);
    });

ideas:

• this test might not be that important, so it could be removed
• conditionally perform this test if the account was actually created

[github-actions]

Preview url: https://67ae3b0d086c6804eba75923--catcolab.netlify.app

[epatters]

Thanks, this will notably improve the robustness of the tests!

• To your question about the test that now sometimes fails, I'm fine with just deleting it since get_active_user_profile will still be tested elsewhere, which seems the most important thing.
• As a GitHub thing, if you write "Closes [my issue number]" instead of "Addresses [my issue number]", merging the PR will automatically close the issue, which is convenient