update changelogs

Author: dsinghvi

fern/products/sdks/overview/typescript/changelog/2025-08-22.mdx

@@ -0,0 +1,23 @@
+## 2.9.1
+**`(fix):`** Introduce a custom configuration called `flattenRequestParameters` which collapses referenced bodies into the 
+request instead of nesting under a body key. 
+
+**Before**: 
+```ts
+client.users.create({
+  userId: "...",
+  body: {
+    "name": "Joe Scott"
+  }
+});
+```
+
+**After** 
+```ts
+client.users.create({
+  userId: "...",
+  "name": "Joe Scott"
+});
+```
+
+