Add reflection hints for native-image support

[violetagg]

native-image support is needed only for 3.5.x version

Fixes #3321

[chemicL]

Thanks @violetagg for adding the hints! Is there any way to have a self-contained validation within the reactor-core project for this or is spring smoke test (https://github.com/spring-projects/spring-aot-smoke-tests) the go-to validation mechanism? Do you think adding the reference to that repository somewhere in the documentation would be beneficial?

[violetagg]

Thanks @violetagg for adding the hints! Is there any way to have a self-contained validation within the reactor-core project for this or is spring smoke test (https://github.com/spring-projects/spring-aot-smoke-tests) the go-to validation mechanism? Do you think adding the reference to that repository somewhere in the documentation would be beneficial?

It would be better Reactor Core to provide tests

As examples one can use
https://github.com/spring-projects/spring-aot-smoke-tests
https://github.com/oracle/graalvm-reachability-metadata

[chemicL]

I created an issue (#3326) to the backlog so we can add the tests but not block rolling out the hints in the next release.

[violetagg]

@chemicL @OlegDokuka Thanks for the review!