add support for previewing pages

web/src/app/client.ts

@@ -3,9 +3,15 @@ import "server-only";
 import { cacheExchange, createClient, fetchExchange } from "@urql/core";
 import { registerUrql } from "@urql/next/rsc";
 
+const wagtailBaseUrl = process.env.WAGTAIL_BASE_URL;
+if (!wagtailBaseUrl) {
+  throw new Error("WAGTAIL_BASE_URL is not set");
+}
+const graphqlEndpoint = `${wagtailBaseUrl.replace(/\/$/, "")}/api/graphql/`;
+
 const makeClient = () => {
   return createClient({
-    url: process.env.GRAPHQL_ENDPOINT ?? "",
+    url: graphqlEndpoint,
     exchanges: [cacheExchange, fetchExchange],
     // requestPolicy: "network-only",
     fetchOptions: { next: { revalidate: 0 } },