feat: warn when GET method has unannotated parameters

[dkswnkk]

Summary

This PR addresses issue #1191 by adding a warning when a @FeignClient method is declared as GET but has one or more parameters that are not annotated with any supported HTTP binding annotations (e.g., @RequestParam, @RequestHeader, @PathVariable, @SpringQueryMap, etc.).

Context

When no annotations are present, Feign may attempt to treat those parameters as a request body. For GET methods, this leads to a body-less POST due to underlying HTTP client behavior (e.g., HttpURLConnection), which causes a discrepancy:

• The client logs show the request as GET
• The server receives the request as a POST
• No request body is actually sent (Content-Length: 0)

This is difficult to debug and confusing in real-world applications.

Related core issue: OpenFeign/feign#2872

Implementation Details

• Added logic in SpringMvcContract#parseAndValidateMetadata() to check for:
  • Method is declared as GET
  • Method has parameters
  • None of the parameters have HTTP-related annotations
• If so, a warning is logged via SLF4J:

[OpenFeign Warning] Feign method 'public abstract Response com.example.Client.getSomething(java.lang.String)' is declared as GET with parameters, but none of the parameters are annotated (e.g. @RequestParam, @RequestHeader, @PathVariable, etc). This may result in fallback to POST at runtime. Consider explicitly annotating parameters.

[OlgaMaciaszek]

Hello @dkswnkk, thanks for submitting the PR. Have added a comment. Please address it.

[OlgaMaciaszek]

Please use if (LOG.isWarnEnabled())[...]

[dkswnkk]

Thank you for your feedback.
I've updated the code to include the LOG.isWarnEnabled() check as you suggested.
Let me know if you have any further comments!

[OlgaMaciaszek]

LGTM.