OpenApi spec not generated from interfaces

[v3rm0n]

I created a new issue for this since it didn't fit the Kotlin issue where I mentioned this. I found out why VaadinService annotation doesn't work with interfaces. Basically javaparser thinks that interface methods are package private by default, which is incorrect. Issue in javaparser is here https://github.com/javaparser/javaparser/issues/2043 Code affected is here https://github.com/vaadin/vaadin-connect/blob/master/vaadin-connect-maven-plugin/src/main/java/com/vaadin/connect/plugin/generator/OpenApiObjectGenerator.java#L390

Current workaround is to just mark your interface methods as public, even though your IDE will probably complain :)