Add release notes for 2.5.1 (#364)

content/release-notes/2.5.1.md

@@ -0,0 +1,19 @@
+---
+title: Haystack 2.5.1
+description: Release notes for Haystack 2.5.1
+toc: True
+date: 2024-09-10
+last_updated: 2024-09-10
+tags: ["Release Notes"]
+link: https://github.com/deepset-ai/haystack/releases/tag/v2.5.1
+---
+
+### ⚡️ Enhancement Notes
+
+- Add `default_headers` init argument to `AzureOpenAIGenerator` and `AzureOpenAIChatGenerator`
+
+### 🐛 Bug Fixes
+
+- Fix the Pipeline visualization issue due to changes in the new release of Mermaid
+- Fix `Pipeline` not running Components with Variadic input even if it received inputs only from a subset of its senders
+- The `from_dict` method of `ConditionalRouter` now correctly handles the case where the `dict` passed to it contains the key `custom_filters` explicitly set to `None`. Previously this was causing an `AttributeError`