Resolve startup warning "An illegal reflective access operation has occurred"

This warning is printed during startup:

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.google.inject.internal.cglib.core.$ReflectUtils$1 (file:/home/ljdelight/.cache/coursier/v1/https/repo1.maven.org/maven2/com/google/inject/guice/4.2.3/guice-4.2.3.jar) to method java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int,java.security.ProtectionDomain)
WARNING: Please consider reporting this to the maintainers of com.google.inject.internal.cglib.core.$ReflectUtils$1
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

It's not a problem with Java 11 but it could block upgrading to JDK17 or JDK21. Easy attempt at a solution is upgrading guice (from guice-4.2.3.jar to later), but this needs caution to not break Playframework

Start by locating the Guice 4.2.3 dependency and the application startup entry point, then reproduce the warning on Java 11, 17, and 21. Check the Play Framework compatibility implications of a Guice upgrade; done means startup no longer emits the illegal reflective access warning without breaking application behavior.