Some of the work will already have been performed in HSEARCH-3514. But we still need to:
Switch to JDK11 for our build, so that module descriptors are actually bundled with released JARs. We will need multi-release JARs for this to work, otherwise module-info.class files will make applications running on Java 8 crash.
Double-check we properly test compatibility with Java modules. In particular, check that a Hibernate Search application can be started with Hibernate Search packaged as Java 9 modules, and that no "split package" errors occur.
Fix any problems related to running Hibernate Search as a Java module.