SDK does not allow to overwrite field of core collection

Describe the Improvement

In my application, I know that a user will always have an email because that is the only way I allow to authenticate. So I want to override the email field of the directus_users core collection to be string instead of string | null. Unfortunately this does not work.

Here is a code example that can be used to reproduce the "problem":

import { createDirectus, readUsers, rest } from '@directus/sdk';

interface CustomUser {
  email: string;
}

interface Collections {
  directus_users: CustomUser;
}

const client = createDirectus<Collections>('URL').with(rest());

const users = await client.request(readUsers({ fields: ['email'] }));

const email = users[0]?.email; // string | null