Create a checkout session to upgrade to a new subscription tier
Authentication via JWT token or API key. JWT: Get from Veryfront dashboard. API Key: Format "vf_
Subscription tier to upgrade to. "professional" is an alias for "pro".
free, pro, enterprise, professional "pro"
Billing cycle
monthly, yearly "monthly"
Seat quantity for licensed subscriptions
x >= 13
URL to redirect to after successful payment
URL to redirect to if payment is cancelled