PipelineTask: load observers from PIPECAT_OBSERVER_FILES

CHANGELOG.md

@@ -9,6 +9,17 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- Added support for loading external observers. You can now register custom
+  pipeline observers by setting the `PIPECAT_OBSERVER_FILES` environment
+  variable. This variable should contain a colon-separated list of Python files
+  (e.g. `export PIPECAT_OBSERVER_FILES="observer1.py:observer2.py:..."`). Each
+  file must define a function with the following signature:
+
+  ```python
+  async def create_observers(task: PipelineTask) -> Iterable[BaseObserver]:
+      ...
+  ```
+
 - Added support for new sonic-3 languages in `CartesiaTTSService` and
   `CartesiaHttpTTSService`.