Update product plan.

curl --request POST \
     --url https://app.amberflo.io/payments/pricing/amberflo/account-pricing/product-plans \
     --header 'accept: application/json' \
     --header 'content-type: application/json' \
     --data '{
     "entitlements": [
     {
     "id": "",
     "apiName": ""
     }
     ],
     "planGenerator": {
     "type": "custom_pricing_plan",
     "id": "",
     "billingPeriod": {},
     "planName": "",
     "entitlements": [
     {
     "id": "",
     "apiName": ""
     }
     ],
     "priceGenerators": {
     "dimensionKeys": [],
     "productItemId": "",
     "priceTiers": [
     {
     "leafNodeType": ""
     }
     ],
     "type": "cost_plus_dimension"
     },
     "invoiceBasedFees": {
     "type": "constant_invoice_ratio_fee"
     }
     }
     }'