Show placeholder message for /chechout and adjust api fetcher type

framework/spree/api/endpoints/checkout/index.ts

@@ -1 +1,23 @@
-export default function noopApi(...args: any[]): void {}
+import { createEndpoint } from '@commerce/api'
+import type { CommerceAPI } from '@commerce/api'
+import type { GetAPISchema } from '@commerce/api'
+import checkoutEndpoint from '@commerce/api/endpoints/checkout'
+import type { CheckoutSchema } from '@commerce/types/checkout'
+import type { SpreeApiProvider } from '@framework/api'
+import checkout from './checkout'
+
+export type CheckoutAPI = GetAPISchema<
+  CommerceAPI<SpreeApiProvider>,
+  CheckoutSchema
+>
+
+export type CheckoutEndpoint = CheckoutAPI['endpoint']
+
+export const handlers: CheckoutEndpoint['handlers'] = { checkout }
+
+const checkoutApi = createEndpoint<CheckoutAPI>({
+  handler: checkoutEndpoint,
+  handlers,
+})
+
+export default checkoutApi