feat(forwarder/sniffer): add HTTP request body rewriting, deprecate rewriteBody in favor of rewriteResponseBody

- Add RewriteRequestBody field to HTTPNodeConfig (yaml: rewriteRequestBody)
- Add RewriteRequestBody field to HTTPNodeSettings in core chain
- Add rewriteReqBody function symmetric to rewriteRespBody in sniffer_rewrite.go
- Wire up rewriteReqBody call in httpRoundTrip before body wrapping for recording
- Add new RewriteResponseBody config field, deprecate old RewriteBody
- Parse both RewriteRequestBody and RewriteResponseBody in node config parsing
- Add 10 test cases covering nil, skip, content-type filter, and chained rewrites
- Bump core dependency to v0.4.1
- Fix: clone response header map in internal/util/sniffing/sniffer_http.go

internal/util/forwarder/sniffer_http.go

@@ -290,6 +290,7 @@ func (h *Sniffer) httpRoundTrip(ctx context.Context, rw, cc io.ReadWriteCloser,
 
 	var responseHeader map[string]string
 	var respBodyRewrites []chain.HTTPBodyRewriteSettings
+	var reqBodyRewrites []chain.HTTPBodyRewriteSettings
 	if httpSettings := node.Options().HTTP; httpSettings != nil {
 		if auther := httpSettings.Auther; auther != nil {
 			username, password, _ := req.BasicAuth()
@@ -325,6 +326,14 @@ func (h *Sniffer) httpRoundTrip(ctx context.Context, rw, cc io.ReadWriteCloser,
 
 		responseHeader = httpSettings.ResponseHeader
 		respBodyRewrites = httpSettings.RewriteResponseBody
+		reqBodyRewrites = httpSettings.RewriteRequestBody
+	}
+
+	// Rewrite request body before wrapping for recording,
+	// so the recorder sees the rewritten content.
+	if err = rewriteReqBody(req, reqBodyRewrites...); err != nil {
+		log.Errorf("rewrite request body: %v", err)
+		return
 	}
 
 	if bodySize := clampBodySize(h.RecorderOptions); bodySize > 0 && req.Body != nil {