feat(API): Add gas-prices endpoint

Can be used to determine what gas price the API is computing

api/gas-prices.ts

@@ -0,0 +1,43 @@
+import { VercelResponse } from "@vercel/node";
+import {
+  getLogger,
+  handleErrorCondition,
+  latestGasPriceCache,
+  sendResponse,
+} from "./_utils";
+import { TypedVercelRequest } from "./_types";
+
+import mainnetChains from "../src/data/chains_1.json";
+
+const chains = mainnetChains;
+
+const handler = async (
+  _: TypedVercelRequest<Record<string, never>>,
+  response: VercelResponse
+) => {
+  const logger = getLogger();
+
+  try {
+    const gasPrices = await Promise.all(
+      chains.map(({ chainId }) => {
+        return latestGasPriceCache(chainId).get();
+      })
+    );
+    const responseJson = Object.fromEntries(
+      chains.map(({ chainId }, i) => [chainId, gasPrices[i]])
+    );
+
+    logger.debug({
+      at: "GasPrices",
+      message: "Response data",
+      responseJson,
+    });
+    // Respond with a 200 status code and 10 seconds of cache with
+    // 45 seconds of stale-while-revalidate.
+    sendResponse(response, responseJson, 200, 10, 45);
+  } catch (error: unknown) {
+    return handleErrorCondition("gas-prices", response, logger, error);
+  }
+};
+
+export default handler;