Add invoke mediator id to function stack

Author: thuva9872

modules/core/src/main/java/org/apache/synapse/mediators/template/TemplateContext.java

@@ -65,6 +65,7 @@ public class TemplateContext {
     public TemplateContext(String name, Collection<TemplateParam> parameters) {
         this.fName = name;
         this.parameters = parameters;
+        addInvokeMediatorIDParam();
         mappedValues = new HashMap();
     }
 
@@ -118,6 +119,11 @@ public void setupParams(MessageContext synCtxt) {
         }
     }
 
+    private void addInvokeMediatorIDParam() {
+
+        parameters.add(new TemplateParam(SynapseConstants.INVOKE_MEDIATOR_ID, false, null));
+    }
+
     private ResolvedInvokeParam getEvaluatedInvokeParam(MessageContext synCtx, String parameterName,
                                                         InvokeParam propertyValue) {