bugfix(@nestjs/common) FileInterceptor overrides multiple options

Author: kamilmysliwiec

src/common/interceptors/file.interceptor.ts

@@ -2,9 +2,10 @@ import * as multer from 'multer';
 import { NestInterceptor } from './../interfaces/nest-interceptor.interface';
 import { Observable } from 'rxjs/Observable';
 import { MulterOptions } from '../interfaces/external/multer-options.interface';
+import { mixin } from '../decorators/core/component.decorator';
 
 export function FileInterceptor(fieldName: string, options?: MulterOptions) {
-  const Interceptor = class implements NestInterceptor {
+  return mixin(class implements NestInterceptor {
     readonly upload = multer(options);
 
     async intercept(
@@ -17,6 +18,5 @@ export function FileInterceptor(fieldName: string, options?: MulterOptions) {
       );
       return stream$;
     }
-  };
-  return Interceptor;
+  });
 }