replace template_spec test with config_variables test

[khassel]

After introducing new config loading this PR replaces the obsolete template test with a config test.

[KristjanESPERANTO]

I'm not entirely sure, but I think the tests might not properly validate variable substitution? 🤔

The current tests check that logLevel and ipWhitelist equal the defaults, but the .env values are set such that they produce exactly those defaults after substitution:

• ["INFO", "LOG", "WARN", "ERROR"] = default
• ["127.0.0.1", "::ffff:127.0.0.1", "::1"] = default

These tests would pass even if substitution was broken. A test for timeFormat would be better since it's the only value that differs from the default:

it("config.timeFormat should be 12 from MM_TIME_FORMAT variable", async () => {
    expect(config.timeFormat).toBe(12); // default is 24
});

This should better verify that substitution works. WDYT?

[KristjanESPERANTO]

By the way: I just wanted to say that I'm really excited that we can now hide the secrets from the front end 😃