Auto-extract value from ParamFlowArgument when blocked in ParamFlowSlot (alibaba#2776)

* Assign actual value with the result of paramFlowKey method

Author: benyamin2014

sentinel-extension/sentinel-parameter-flow-control/src/main/java/com/alibaba/csp/sentinel/slots/block/flow/param/ParamFlowSlot.java

@@ -82,6 +82,10 @@ void checkFlow(ResourceWrapper resourceWrapper, int count, Object... args) throw
                 String triggeredParam = "";
                 if (args.length > rule.getParamIdx()) {
                     Object value = args[rule.getParamIdx()];
+                    // Assign actual value with the result of paramFlowKey method
+                    if (value instanceof ParamFlowArgument) {
+                        value = ((ParamFlowArgument) value).paramFlowKey();
+                    }
                     triggeredParam = String.valueOf(value);
                 }
                 throw new ParamFlowException(resourceWrapper.getName(), triggeredParam, rule);