add OriginalClassSym

src/decorators/register.ts

 import {
   ClassType,
   GeneratedSym,
+  OriginalClassSym,
   RefSym,
   SchemaClassOptions,
   SchemaOptions,
@@ -227,6 +228,7 @@ export function SchemaClass<T>(originalClass: ClassType<T>) {
     return applySchemaForClass(schema, originalClass, instance, originalObject);
   } as unknown as ClassType<T> & Schema<Partial<T>, T>;
   newClass[GeneratedSym] = schema;
+  newClass[OriginalClassSym] = originalClass;
   Object.defineProperty(newClass, 'name', {
     value: originalClass.name,
   });

src/def/interfaces.ts

@@ -47,3 +47,4 @@ export type SchemaOptionsDict<T> = { [P in keyof T]?: SchemaOptions };
 
 export const RefSym = Symbol('SchemasteryGenRef');
 export const GeneratedSym = Symbol('GeneratedSym');
+export const OriginalClassSym = Symbol('OriginalClassSym');