Allow BindParam on a field

See gh-30947

Author: rstoyanchev

Diff for: spring-web/src/main/java/org/springframework/web/bind/annotation/BindParam.java

@@ -31,7 +31,7 @@
  * @since 6.1
  * @see org.springframework.web.bind.WebDataBinder#construct
  */
-@Target(ElementType.PARAMETER)
+@Target({ElementType.PARAMETER, ElementType.FIELD})
 @Retention(RetentionPolicy.RUNTIME)
 @Documented
 public @interface BindParam {