feat: complete saleor core extensions app with React email templates

- Order confirmation, shipped, and cancelled email templates
- Uses @react-email/components for professional HTML emails
- Sends admin and customer notifications
- Integrates with Resend for email delivery
- Webhook handlers for ORDER_CREATED, ORDER_FULFILLED, ORDER_CANCELLED
- Docker image optimized for production
- Persistent auth data storage via PVC

src/pages/api/server-widget.ts

@@ -0,0 +1,41 @@
+import { NextApiHandler } from "next";
+import { ExtensionPOSTAttributes } from "@saleor/app-sdk/types";
+import { verifyJWT } from "@saleor/app-sdk/auth";
+import { createClient } from "@/lib/create-graphq-client";
+import { ProductTimestampsDocument } from "../../../generated/graphql";
+
+const handler: NextApiHandler = async (req, res) => {
+  const { appId, accessToken, saleorApiUrl, ...contextParams } =
+    req.body as ExtensionPOSTAttributes;
+
+  res.setHeader("Content-Type", "text/plain");
+
+  try {
+    await verifyJWT({
+      appId,
+      token: accessToken,
+      saleorApiUrl,
+    });
+  } catch (e) {
+    return res.status(401).send("Not authorized");
+  }
+
+  if (!contextParams.productId) {
+    return res.status(200).send("Missing product ID");
+  }
+
+  const client = createClient(saleorApiUrl, async () => ({ token: accessToken }));
+  const productTimestamps = await client.query(ProductTimestampsDocument, {
+    id: contextParams.productId,
+  });
+
+  if (productTimestamps.data?.product) {
+    return res
+      .status(200)
+      .send(
+        `This product was created at ${productTimestamps.data.product.created} and last updated at ${productTimestamps.data.product.updatedAt}`
+      );
+  }
+};
+
+export default handler;