Multiple Email

Problem/Motivation

The html <input type='email' multiple> specification allows adding multiple addresses separated by commas, but the validation marks multiple email addresses as an invalid email.

Steps to reproduce

create a form field with the multiple attribute

$form['email'] => [
  '#type' => 'email',
  '#title' => 'test',
  '#attributes' => [
    'multiple'=>TRUE,
  ],
];
return $form;

this properly creates an html email input, but the validation fails when you enter an email in the format test@email.com,test@email.org

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes