Update changelogs from fern repo (#4478)

Co-authored-by: iamnamananand996 <31537362+iamnamananand996@users.noreply.github.com>

Author: fern-support

fern/products/sdks/overview/rust/changelog/2026-03-21.mdx

@@ -1,3 +1,13 @@
+## 0.24.0
+**`(feat):`** Improve discriminated union design with inlined variants and constructors. When an inner
+type is only referenced by a single union variant, its fields are now inlined directly into
+the enum variant instead of using a wrapper struct with `#[serde(flatten)]`. All enum
+variants now include `#[non_exhaustive]` for forward compatibility, and constructor methods
+are generated for every variant (required since `#[non_exhaustive]` prevents direct
+construction outside the crate). Empty variants use struct syntax (`Variant {}`) instead
+of unit syntax.
+
+
 ## 0.23.0
 **`(feat):`** Generate builders for all struct types. The builder pattern is inspired by
 other popular Rust SDKs (e.g. AWS), so that users now have the option between the