docs: add description of returning different status codes

docs/content/1.docs/2.guide/2.directory-structure/1.server.md

@@ -163,6 +163,37 @@ export default defineEventHandler((event) => {
 })
 ```
 
+### Error handling
+
+If no errors are thrown a status code of `200 OK` will be returned. Any uncaught errors will return a `500 Internal Server Error` HTTP Error.
+
+To return other error codes, throw an exception with `createError`
+
+```ts [server/api/validation/[id].ts]
+export default defineEventHandler((event) => {
+  const id = parseInt(event.context.params.id) as number
+  if (!Number.isInteger(id)) {
+    throw createError({
+      statusCode: 400,
+      statusMessage: 'ID should an integer',
+    })
+  }
+  return 'All good'
+})
+```
+
+### Returning other status codes
+
+To return other status codes, you can use the `setResponseStatus` utility.
+
+For example to return `202 Accepted`
+
+```ts [server/api/validation/[id].ts]
+export default defineEventHandler((event) => {
+  setResponseStatus(event, 202)
+})
+```
+
 ### Accessing Runtime Config
 
 ```ts [server/api/foo.ts]