build: upgrade minimum compatible version to Java 11

[keturn]

This updates the project's gradle configuration to use the Java 11 compatibility level. IntelliJ IDEA will recognize this configuration when determining which languages features are available.

Requires

• build: build using a java 11 toolchain #4942
  CI must have a Java 11 environment to build in before we have developers making commits for Java 11.

[keturn]

Java Version

[keturn]

Build passed its unit tests, but crashed during the javadoc task? That's certainly not what I expected. Maybe I didn't put enough RAM in the pod configuration?

(Yet unknown if integration tests pass, because that stage only runs after javadoc completes.)

[keturn]

• CI test run 4: re-build with the same configuration. Failed in an earlier stage.
• CI test run 5: increased pod memory limit to 6Gi, matching the old java8 precached pod configuration. Build succeeded.

[keturn]

The LGTM service has a Java 8 build environment.

There's been no news posted to their blog since they were acquired by GitHub two years ago.
I can't connect to their discourse forum.

Would we be okay with dropping the LGTM GitHub integration?

🔗 Discord Thread

[keturn]

I really expected to run in to the #3992 failure at this point, but it looks like all the tests are passing in this run, so hooray?

[keturn]

wait, I do get that failure locally. 😕

[keturn]

I think we have not been running the TypeHandlerLibrary tests ever since the unitTest / integrationTest split 😢