Paypal Express Checkout - closes #10531

[ornicar]

A whole new mess of monthly one-time payments, recurring payments, lifetime payments, currencies, gifts, subscription canceling, credit-card update, amount update, interoperability with stripe and compatibility with legacy paypal subscriptions. Yay

[ornicar]

Create products (change hostname for prod)

curl -X POST https://api-m.sandbox.paypal.com/v1/catalogs/products \
-H "Content-Type: application/json" \
-H "Authorization: Bearer $paypal_token" \
-d '{
  "id": "PATRON-GIFT",
  "name": "Gift Patron",
  "description": "Gift Patron wings to another player.",
  "type": "DIGITAL",
  "category": "SOFTWARE"
}'

curl -X POST https://api-m.sandbox.paypal.com/v1/catalogs/products \
-H "Content-Type: application/json" \
-H "Authorization: Bearer $paypal_token" \
-d '{
  "id": "PATRON-MONTH",
  "name": "Monthly Patron",
  "description": "Support Lichess and get Patron wings. The subscription is renewed every month.",
  "type": "DIGITAL",
  "category": "SOFTWARE"
}'

curl -X POST https://api-m.sandbox.paypal.com/v1/catalogs/products \
-H "Content-Type: application/json" \
-H "Authorization: Bearer $paypal_token" \
-d '{
  "id": "PATRON-ONETIME",
  "name": "One-time Patron",
  "description": "Support Lichess and get the Patron wings for one month. Will not renew automatically.",
  "type": "DIGITAL",
  "category": "SOFTWARE"
}'

[ornicar]

curl -X POST https://api-m.sandbox.paypal.com/v1/billing/plans \
-H "Content-Type: application/json" \
-H "Authorization: Bearer $paypal_token" \
-d '{
  "product_id": "PATRON-MONTH",
  "name": "Monthly Patron",
  "description": "Support Lichess and get Patron wings. The subscription is renewed every month.",
  "status": "ACTIVE",
  "billing_cycles": [
    {
      "frequency": {
        "interval_unit": "MONTH",
        "interval_count": 1
      },
      "tenure_type": "REGULAR",
      "sequence": 1,
      "total_cycles": 0,
      "pricing_scheme": {
        "fixed_price": {
          "value": "5",
          "currency_code": "USD"
        }
      }
    }
  ],
  "payment_preferences": {
    "auto_bill_outstanding": true,
    "payment_failure_threshold": 3
  }
}'