add support for sealed response interfaces for spring-declarative-http-interface

[tempacc21]

fixes #23548

#23003 Added support for sealed response interfaces, but it is not supported for spring-declarative-http-interface

This PR adds support for it. I had some trouble running the mvnw clean package command locally on my mac, but KotlinSpringServerCodegenTest passes

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Summary by cubic

Adds sealed response interface support to Kotlin Spring spring-declarative-http-interface when useSealedResponseInterfaces is enabled, so generated APIs can return sealed interfaces instead of concrete models. Fixes #23548.

• New Features
  • Applies vendorExtensions.x-sealed-response-interface to return types for maps, arrays, and single results, with or without ResponseEntity, Reactor, or coroutines.
  • Adds a generator test validating ResponseEntity<CreateUserResponse> and ResponseEntity<GetUserResponse> outputs.

^{Written for commit 599f102. Summary will update on new commits.}

[tempacc21]

Hey, would love a review @karismann @Zomzog @andrewemery @4brunu @stefankoppier @e5l @dennisameling

[cubic-dev-ai]

No issues found across 2 files