Changelog: migration advice on beforeUpload.

CHANGELOG.md

@@ -21,6 +21,38 @@
   - Depending on the type, only the parsers needed for certain endpoint are processed;
   - This reverts changes on muting uploader logs related to non-eligible requests made in v18.5.2 (all eligible now).
 
+```ts
+import createHttpError from "http-errors";
+import { createConfig } from "express-zod-api";
+
+const before = createConfig({
+  server: {
+    upload: {
+      beforeUpload: ({ app, logger }) => {
+        app.use((req, res, next) => {
+          if (req.is("multipart/form-data") && !canUpload(req)) {
+            return next(createHttpError(403, "Not authorized"));
+          }
+          next();
+        });
+      },
+    },
+  },
+});
+
+const after = createConfig({
+  server: {
+    upload: {
+      beforeUpload: ({ request, logger }) => {
+        if (!canUpload(request)) {
+          throw createHttpError(403, "Not authorized");
+        }
+      },
+    },
+  },
+});
+```
+
 ## Version 18
 
 ### v18.5.2