Update changelogs from fern repo (#4573)

Co-authored-by: aditya-arolkar-swe <13171215+aditya-arolkar-swe@users.noreply.github.com>

Author: fern-support

fern/products/sdks/overview/python/changelog/2026-03-26.mdx

@@ -0,0 +1,9 @@
+## 5.0.8
+**`(fix):`** Eliminate Pydantic v2 deprecation warnings in `UniversalBaseModel`. Under Pydantic v2,
+the class-based `Config` pattern with `smart_union` and `allow_population_by_field_name`
+emits deprecation warnings. `UniversalBaseModel` now uses `model_config: ConfigDict` with
+`populate_by_name=True`, `validate_by_name=True`, and `validate_by_alias=True` (for v2.11+
+support) for v2, and a custom `@model_serializer` for datetime serialization instead of
+the deprecated `json_encoders`. Pydantic v1 continues to use the original class-based Config.
+
+