web: centralize prop fetching for live + preview, fix preview banner breakage

web/src/app/[...url]/page.tsx

@@ -1,11 +1,10 @@
 import { graphql } from "@/gql";
-import { GenericFragment } from "@/gql/graphql";
 import { getClient } from "@/app/client";
 import { Metadata, ResolvingMetadata } from "next";
 import { notFound } from "next/navigation";
 import {
   GenericPageView,
-  genericPageByUrlPathQuery,
+  loadGenericPageProps,
 } from "@/components/general/GenericPageView";
 import { getSeoMetadata } from "@/lib/seo";
 
@@ -53,38 +52,14 @@ export async function generateMetadata(
   parent: ResolvingMetadata
 ): Promise<Metadata | null> {
   const { url } = await params;
-  const urlPath = getWagtailUrlPath(url);
-  const { data, error } = await getClient().query(genericPageByUrlPathQuery, {
-    urlPath: urlPath,
-  });
-
-  if (error) {
-    throw new Error(error.message);
-  }
-  if (!data?.page) {
-    return null;
-  }
-
-  const page = data.page as GenericFragment;
-  const metadata = await getSeoMetadata(page, parent);
-  return metadata;
+  const props = await loadGenericPageProps({ urlPath: getWagtailUrlPath(url) });
+  if (!props) return null;
+  return getSeoMetadata(props.page, parent);
 }
 
 export default async function Page({ params }: { params: Params }) {
   const { url } = await params;
-  const urlPath = getWagtailUrlPath(url);
-  const { data, error } = await getClient().query(genericPageByUrlPathQuery, {
-    urlPath: urlPath,
-  });
-  if (error) {
-    throw new Error(error.message);
-  }
-
-  if (!data?.page) {
-    return notFound();
-  }
-
-  const page = data?.page as GenericFragment;
-
-  return <GenericPageView page={page} />;
+  const props = await loadGenericPageProps({ urlPath: getWagtailUrlPath(url) });
+  if (!props) return notFound();
+  return <GenericPageView {...props} />;
 }