non-null license keys

[overheadhunter]

@PostConstruct LicenseHolder.init() is changed to a normal method LicenseHolder. ensureLicenseExists(), which is called during application start in the newly added Quarkus Main class:

hub/backend/src/main/java/org/cryptomator/hub/Main.java

Lines 18 to 28 in cde9e6c

	@Override
	public int run(String... args) throws Exception {
	try {
	license.ensureLicenseExists();
	} catch (RuntimeException e) {
	LOG.error("Failed to validate license, shutting down...", e);
	return 1;
	}
	Quarkus.waitForExit();
	return 0;
	}

In other words: The application won't start without a license. But fear not, it is able to request a free license autonomously. In other words, if it is running, a license does exist, which reduces a lot of branching.