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

config/parsing/node/parse.go

@@ -231,6 +231,24 @@ func ParseNode(hop string, cfg *config.NodeConfig, log logger.Logger) (*chain.No
 				})
 			}
 		}
+		for _, v := range cfg.HTTP.RewriteResponseBody {
+			if pattern, _ := regexp.Compile(v.Match); pattern != nil {
+				settings.RewriteResponseBody = append(settings.RewriteResponseBody, chain.HTTPBodyRewriteSettings{
+					Type:        v.Type,
+					Pattern:     pattern,
+					Replacement: []byte(v.Replacement),
+				})
+			}
+		}
+		for _, v := range cfg.HTTP.RewriteRequestBody {
+			if pattern, _ := regexp.Compile(v.Match); pattern != nil {
+				settings.RewriteRequestBody = append(settings.RewriteRequestBody, chain.HTTPBodyRewriteSettings{
+					Type:        v.Type,
+					Pattern:     pattern,
+					Replacement: []byte(v.Replacement),
+				})
+			}
+		}
 		opts = append(opts, chain.HTTPNodeOption(settings))
 	}