update changelogs

Author: tstanmay13

fern/products/sdks/overview/java/changelog/2025-09-09.mdx

@@ -0,0 +1,25 @@
+## 3.0.0
+**`(break):`** The SDK generator now defaults to forward-compatible enums, providing resilience against new enum variants 
+added on the backend. This is a breaking change that affects the structure of generated enum types.
+
+To revert to the previous behavior with traditional Java enums, add the following configuration to your 
+`generators.yml` file:
+```yaml
+generators:
+  - name: fernapi/fern-java-sdk
+    config:
+      enable-forward-compatible-enums: false
+```
+
+
+**`(feat):`** Forward-compatible enums are now enabled by default. Generated SDKs will no longer throw errors when 
+encountering unknown enum variants, instead handling them gracefully with an UNKNOWN value. This is 
+particularly important for:
+- Mobile applications that cannot be easily updated
+- Maintaining backward compatibility when backend adds new enum values
+- Arrays of enum values where new variants previously caused client failures
+
+With forward-compatible enums, the generated code changes from traditional Java enums to class-based 
+enums that support unknown values through a visitor pattern.
+
+