BillingService Android PurchasePlatformProductAsync Does Not Work

[david-maw]

Attempting to buy something always fails calling PurchasePlatformProductAsync.

Internally QueryProductDetailsAsync always returns "DEVELOPER ERROR: Invalid SKU type: InApp" because .SetProductType("InApp") is used to compose the QueryproductDetails parameter. The fix is to use .SetProductType(BillingClient.ProductType.Inapp) instead - it actually evaluates to "inapp" which the Android Play API recognizes.