UnsupportedClassVersionError when installing DuoOIDCNimbusPlugin with OpenJDK11

[Cantor, Scott]

> there isn't actually a current version of the DuoOIDC plugin that supports
> IdP 4.2.1.

That's true, but only because 4.2 itself became unsupported the instant 4.3 was released so by definition anything older is out of date also.

Out of date doesn't mean it won't work, just that's not supported, because we never support multiple minors. That's why we spend so many hours trying to prevent regressions on upgrades, because it's expected that upgrading minors should be a non-event.

-- Scott