Drops @SpringBootTest + PostgresContainerConfig + @MockitoBean S3Client in
favour of Spring's Binder API against application.yaml. The new test binds
the property into the typed ServerProperties.ForwardHeadersStrategy enum,
so typos (`nativ`, `Native`, `framework `) and future enum renames fail
the build with BindException — addresses the silent-coercion concern that
the YAML-string assertion missed.
Verified the test goes red on a typo (BindException: Failed to convert
"nativ" → ForwardHeadersStrategy) and green on `native`.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>