Meter usage with upto

import { x402ResourceServer, HTTPFacilitatorClient } from "@x402/core/server";
import { bazaarResourceServerExtension } from "@x402/extensions/bazaar";
import { UptoStellarServerScheme } from "@rail402.dev/scheme-upto-stellar";
import { describeEndpoint } from "@rail402.dev/sdk";

const USDC = "CBIELTK6YBZJU5UP2WWQEUCYKLPU6AUNZ2BQ4WWFEIE3USCIHMXQDAMA"; // testnet USDC SAC

const x402 = new x402ResourceServer([
  new HTTPFacilitatorClient({ url: "https://facilitator.rail402.dev" }),
]);
x402.register("stellar:*", new UptoStellarServerScheme());
x402.registerExtension(bazaarResourceServerExtension);

// In the paywall route:
"POST /generate": {
  accepts: {
    scheme: "upto",
    network: "stellar:testnet",
    price: { amount: "2000000", asset: USDC }, // ceiling: "2000000" atomic units = 0.20 USDC max
    payTo: process.env.SELLER_ADDRESS,
    maxTimeoutSeconds: 60,
  },
  description: "Generates text and bills for tokens actually produced.",
  mimeType: "application/json",
  extensions: describeEndpoint({
    params: { prompt: { description: "The prompt to generate from.", example: "Summarize this." } },
  }),
}