Automate WordPress-Mailchimp User Sync

I want every new user who registers on my WordPress site (using the Clasima plugin) to be pushed instantly into a specific Mailchimp list without any manual export-import steps. My Mailchimp account is already active; I simply need a clean, reliable bridge between WordPress and Mailchimp.

Here’s what I expect:
• Configure or install the most suitable WordPress plugin—or lightweight custom code if that’s cleaner—to capture the “New user registration” event.
• Map the key user fields (first name, last name, email, plus any standard profile fields I already collect) to the corresponding Mailchimp audience fields.
• Ensure the data transfer uses the Mailchimp API and respects GDPR-friendly opt-in status already gathered during registration.
• Test end-to-end: create a dummy user, confirm the record appears in Mailchimp with correct tags or segments, and provide screenshots or a short Loom video of the working flow.
• Hand over concise setup notes so I can maintain or tweak the integration later.

No need to track profile updates or other activities right now—just the initial registration event is in scope. A straightforward plugin-based solution is welcome as long as it’s secure, lightweight, and maintained, but I’m open to custom code if that proves simpler.

Please deliver a fully functioning sync along with the brief documentation, and be available for a quick round of tweaks if any field mapping needs adjusting after I review the first test.