Allow adding packages to entity scanning without disabling the default scanning

I would like to provide a library that adds JPA entities to the persistence context bootstrapped. Ideally I would like to achieve that without the user having to explicitly configure @EntityScan to include the package of that library solely by registering some auto configuration.

I've tried both @EntityScan on a configuration class and a BeanDefinitionRegistryPostProcessor to trigger EntityScanPackages.register(…) but EntityScanner will only apply the autoconfiguration package as fallback if no entity package is configured at all.

I can see that the semantics of @EntityScan are supposed to stay unchanged. I'd be fine with a programmatic approach, so maybe an explicit method EntityScanPackage.registerAdditional(…) could populate an additional list that EntityScanner adds on top of the defaulted base list?

Start by reading EntityScanPackages.register(…) and EntityScanner, focusing on how the autoconfiguration package is used as a fallback when no entity package is configured. The change would need to preserve @EntityScan semantics while allowing additional packages to be registered and included alongside the default base package; no specific test file is mentioned.