** Place on a method of a FormBean to have it take part in server side validation.
** Validate methods should be static and take a single 'FormField' parameter.
** They should inspect the 'formField.value' and set an 'errMsg' if invalid.
** Example:
**
** pre>
** syntax: fantom
**
** class User {
** Str? name
**
** @Validate { field=#name }
** static Void validateName(FormField formField) {
** if (formField.formValue == "Trisha")
** formField.errMsg = "Ex-girlfriends not allowed!"
** }
** }
** <pre
**
** If '@Validate.field' is 'null' then the first parameter should be 'FormBean':
**
** pre>
** syntax: fantom
**
** @Validate
** static Void validateBean(FormBean formBean) { ... }
** <pre
**
** 'FormBean' validation is performed *after* 'FormField' validation.
**
** Note that validation methods are called using IoC, so services may be passed in as extra method parameters:
**
** pre>
** syntax: fantom
**
** @Validate
** static Void validateName(FormField formField, MyService service) { ... }
** <pre
**
facet class Validate {
** The field this method validates. The validation method will only be called with 'FormFields' that correspond to this field.
**
** If 'null' then the method will be called with a 'FormBean' instance.
const Field? field
}
