feat: turbostarter boilerplate

Production-ready Next.js boilerplate with:
- Runtime env validation (fail-fast on missing vars)
- Feature-gated config (S3, Stripe, email, OAuth)
- Docker + Coolify deployment pipeline
- PostgreSQL + pgvector, MinIO S3, Better Auth
- TypeScript strict mode (no ignoreBuildErrors)
- i18n (en/es), AI modules, billing, monitoring

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/billing/src/providers/lemon-squeezy/checkout.ts

@@ -0,0 +1,129 @@
+import {
+  createCheckout,
+  getCustomer,
+  getOrder,
+} from "@lemonsqueezy/lemonsqueezy.js";
+
+import { HttpStatusCode } from "@turbostarter/shared/constants";
+import { logger } from "@turbostarter/shared/logger";
+import { HttpException } from "@turbostarter/shared/utils";
+
+import { config } from "../../config";
+import { getCustomerByCustomerId, updateCustomer } from "../../lib/customer";
+import { getCustomerByUserId } from "../../server";
+import { getHighestDiscountForPrice } from "../../utils";
+
+import { createOrRetrieveCustomer } from "./customer";
+import { env } from "./env";
+import { toCheckoutBillingStatus } from "./mappers/to-billing-status";
+
+import type { BillingProviderStrategy } from "../types";
+
+export const checkout: BillingProviderStrategy["checkout"] = async ({
+  user,
+  price: { id },
+  redirect,
+}) => {
+  try {
+    const plan = config.plans.find((plan) =>
+      plan.prices.some((p) => p.id === id),
+    );
+
+    const price = plan?.prices.find((p) => p.id === id);
+
+    if (!price || !plan) {
+      throw new HttpException(HttpStatusCode.NOT_FOUND, {
+        code: "billing:error.priceNotFound",
+      });
+    }
+
+    const customer = await createOrRetrieveCustomer({
+      email: user.email,
+      id: user.id,
+    });
+
+    const discount = getHighestDiscountForPrice(price, config.discounts);
+
+    const session = await createCheckout(env.LEMON_SQUEEZY_STORE_ID, id, {
+      checkoutData: {
+        email: customer.attributes.email,
+        name: customer.attributes.name,
+        custom: {
+          user_id: user.id,
+        },
+        ...(discount && { discountCode: discount.code }),
+      },
+      productOptions: {
+        enabledVariants: [Number(id)],
+        redirectUrl: redirect.success,
+      },
+    });
+
+    return { url: session.data?.data.attributes.url ?? null };
+  } catch (e) {
+    logger.error(e);
+    throw new HttpException(HttpStatusCode.INTERNAL_SERVER_ERROR, {
+      code: "billing:error.checkout",
+    });
+  }
+};
+
+export const getBillingPortal: BillingProviderStrategy["getBillingPortal"] =
+  async ({ user }) => {
+    const defaultUrl = `https://${env.LEMON_SQUEEZY_STORE_ID}.lemonsqueezy.com/billing`;
+
+    try {
+      const customer = await getCustomerByUserId(user.id);
+
+      if (!customer) {
+        return {
+          url: defaultUrl,
+        };
+      }
+
+      const lemonCustomer = await getCustomer(customer.customerId);
+
+      const url = lemonCustomer.data?.data.attributes.urls.customer_portal;
+
+      return { url: url ?? defaultUrl };
+    } catch (e) {
+      logger.error(e);
+      throw new HttpException(HttpStatusCode.INTERNAL_SERVER_ERROR, {
+        code: "billing:error.portal",
+      });
+    }
+  };
+
+export const checkoutStatusChangeHandler = async ({ id }: { id: string }) => {
+  const { data } = await getOrder(id);
+
+  const order = data?.data;
+
+  if (!order) {
+    throw new HttpException(HttpStatusCode.NOT_FOUND, {
+      code: "billing:error.orderNotFound",
+    });
+  }
+
+  const customer = await getCustomerByCustomerId(
+    order.attributes.customer_id.toString(),
+  );
+
+  if (!customer) {
+    throw new HttpException(HttpStatusCode.NOT_FOUND, {
+      code: "billing:error.customerNotFound",
+    });
+  }
+
+  const priceId = order.attributes.first_order_item.variant_id.toString();
+  const plan = config.plans.find((p) => p.prices.find((x) => x.id === priceId));
+
+  await updateCustomer(customer.userId, {
+    status: toCheckoutBillingStatus(order.attributes.status),
+    ...(plan && { plan: plan.id }),
+  });
+
+  logger.info(
+    `✅ Checkout status changed for user ${customer.userId} to ${order.attributes.status}`,
+  );
+};