Simplify Websocket Csrf Processor XML Configuration

[evga7]

This PR refactors the class matching logic for CSRF token handshake interceptor registration in MessageSecurityPostProcessor.

Changes

• Replaces multiple else-if conditions checking beanClassName with a single Set<String> lookup
• Introduces CSRF_HANDSHAKE_HANDLER_CLASSES as a static, final, and immutable constant using Collections.unmodifiableSet(...)
• Preserves existing behavior while improving readability and maintainability
• Keeps import statements explicit (avoids wildcard imports)

Why

• Removes duplicate string checks
• Prevents potential copy-paste errors
• Makes it easier to extend or maintain the list of supported handshake handler classes

Let me know if further refinement or test adjustments are needed.

[jzheaux]

Thanks, @evga7 for this cleanup! It'll be merged into main once the build completes.

Let me know if further refinement or test adjustments are needed.

Not at this point, though for future PRs, you can build using:

./gradlew format && ./gradle checkstyleMain checkstyleTest

This will advise you of any formatting or style issues that need addressing.

[evga7]

Thanks for reviewing and merging!
I'll make sure to run ./gradlew format and ./gradlew checkstyleTest in future PRs.