weMail < 2.0.8 - Missing Authorization to Unauthenticated Form Deletion

Description

The weMail - Email Marketing, Lead Generation, Optin Forms, Email Newsletters, A/B Testing, and Automation plugin for WordPress is vulnerable to unauthorized form deletion in all versions up to, and including, 2.0.7. This is due to the `Forms::permission()` callback only validating the `X-WP-Nonce` header without checking user capabilities. Since the REST nonce is exposed to unauthenticated visitors via the `weMail` JavaScript object on pages with weMail forms, any unauthenticated user can permanently delete all weMail forms by extracting the nonce from the page source and sending a DELETE request to the forms endpoint.