Replace HttpServletRequest with minimal header interface in core API

[cuioss-oliver]

Finding H-7 from code-findings.adoc

VertxHttpServletRequestAdapter is an 826-line adapter implementing full HttpServletRequest with 27 methods throwing UnsupportedOperationException. Production usage is headers only (getHeaderNames(), getHeaders()).

Recommendation

Change core API to accept a header map (Map<String, List<String>>) or a minimal interface instead of HttpServletRequest. Delete VertxHttpServletRequestAdapter entirely.

Scope

• Touches the API boundary between core and Quarkus modules
• Affects interceptors, producers, and test mocks
• The adapter is internal (not exposed to application code)