post https://a.klaviyo.com/client/subscriptions/
Create a new subscription for the given list ID and channel:
- Email
email - SMS
phone_number
This endpoint is specifically designed to be called from publicly-browseable, client-side environments only. To create subscriptions from server-based applications, please use POST /api/profile-subscription-bulk-create-jobs
Rate limits:
Burst: 100/s
Steady: 100/m
Scopes:
Subscriptions Write