Summary

• Add japicmp-maven-plugin to enforce binary and source compatibility against the latest released version
• Fix binary incompatibility in Client.Proxied (superclass changed from Client.Default to DefaultClient)
• Remove unnecessary shade, really-executable-jar, and docker plugins from apt-test-generator module
• Mark all graphql module classes as @Experimental

Details

japicmp configuration:

• Breaks the build on binary/source incompatible modifications
• Enforces semantic versioning
• Excludes example modules, benchmark, @feign.Experimental annotated classes, and feign.graphql package
• Skipped for apt-test-generator (build tool, not a library)
• Already respected by quickbuild profile (japicmp.skip=true)

Binary compatibility fix:

• Client.Proxied now extends Client.Default again (instead of DefaultClient directly), preserving the class hierarchy from 13.9

apt-test-generator cleanup:

• Removed shade plugin, really-executable-jar plugin, docker plugin, and docker resource config (dead code — docker directory doesn't even exist)

GraphQL module:

• Added @Experimental to all public classes since the module's API is still evolving

Test plan

• mvn verify -DskipTests passes across all modules (except pre-existing form lombok issue)
• mvn test -pl core,graphql passes