[kotlin-spring] support 'x-operation-extra-annotation' in 'spring-declarative-http-interface'

[Picazsoo]

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Summary by cubic

Adds support for the x-operation-extra-annotation vendor extension in Kotlin Spring spring-declarative-http-interface generation. This lets you inject custom per-operation annotations (e.g., security) into generated API interfaces.

• New Features
  • Renders x-operation-extra-annotation directly above @HttpExchange in generated methods.
  • Added test verifying output with @Secured("ROLE_ADMIN") on getInventory.

^{Written for commit 9a82e02. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 2 files

_{Re-trigger cubic}