Authenticate against Yotpo Loyalty & Referrals and create/fetch customer loyalty records

Steps

1. Retrieve your GUID and API key from the Yotpo Loyalty dashboard (Settings > General Settings).
2. Send both values on every request (commonly as x-guid and x-api-key), confirming the exact header/query placement against the live endpoint reference for each call you build.
3. POST /api/v2/customers to create or upsert a customer record, supplying email plus optional profile fields; note that tags on this call overwrite rather than merge with existing tags.
4. GET /api/v2/customers with exactly one identifying parameter (customer_email, customer_id, pos_account_id, or phone_number) to fetch point balance, referral link, and points-expiration data.
5. Pass with_history explicitly on the fetch call rather than relying on its default, since the default has been inconsistently documented.