[Fix #1456] Change WorkflowDefinitionID implementation

Fix #1456

Signed-off-by: fjtirado <ftirados@ibm.com>

Author: fjtirado

impl/core/src/main/java/io/serverlessworkflow/impl/WorkflowDefinitionId.java

@@ -32,6 +32,11 @@ public static WorkflowDefinitionId of(Workflow workflow) {
   public static WorkflowDefinitionId fromName(String name) {
     return new WorkflowDefinitionId(DEFAULT_NAMESPACE, name, DEFAULT_VERSION);
   }
+  
+  @Override
+  public String toString() {
+	  return toString(":");
+  }
 
   public String toString(String separator) {
     return namespace + separator + name + separator + version;