Tainacan <= 1.0.1 - Missing Authorization to Unauthenticated Arbitrary Metadata Section Creation

The Tainacan plugin for WordPress is vulnerable to unauthorized metadata section creation due to missing authorization checks in all versions up to, and including, 1.0.1. This is due to the `create_item_permissions_check()` function unconditionally returning true, which bypasses authentication and authorization validation. This makes it possible for unauthenticated attackers to create arbitrary metadata sections for any collection via the public REST API granted they can access the WordPress site.