Fix audience validation issues

internal/util/rpc.go

@@ -0,0 +1,39 @@
+package util
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"net/http"
+
+	logger "github.com/wso2/open-mcp-auth-proxy/internal/logging"
+)
+
+type RPCEnvelope struct {
+	Method string `json:"method"`
+	Params any    `json:"params"`
+	ID     any    `json:"id"`
+}
+
+// This function parses a JSON-RPC request from an HTTP request body
+func ParseRPCRequest(r *http.Request) (*RPCEnvelope, error) {
+	bodyBytes, err := io.ReadAll(r.Body)
+	if err != nil {
+		return nil, err
+	}
+	r.Body = io.NopCloser(bytes.NewBuffer(bodyBytes))
+
+	if len(bodyBytes) == 0 {
+		return nil, nil
+	}
+
+	var env RPCEnvelope
+	dec := json.NewDecoder(bytes.NewReader(bodyBytes))
+	if err := dec.Decode(&env); err != nil && err != io.EOF {
+		logger.Warn("Error parsing JSON-RPC envelope: %v", err)
+		return nil, err
+	}
+
+	logger.Info("JSON-RPC method = %q", env.Method)
+	return &env, nil
+}