Add support for OpenTelemetry tracing (#1729)

* Also added TurnTrackingObserver, TurnTraceObserver, foundational 29, open-telemetry-example

CHANGELOG.md

@@ -16,6 +16,36 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   `CancelFrame` are pushed from the beginning of the pipeline and finally
   `FrameProcessor.cleanup()` is called.
 
+- Added support for OpenTelemetry tracing in Pipecat. This initial
+  implementation includes:
+
+  - A `setup_tracing` method where you can specify your OpenTelemetry exporter
+  - Service decorators for STT (`@traced_stt`), LLM (`@traced_llm`), and TTS
+    (`@traced_tts`) which trace the execution and collect properties and
+    metrics (TTFB, token usage, character counts, etc.)
+  - Class decorators that provide execution tracking; these are generic and can
+    be used for service tracking as needed
+  - Spans that help track traces on a per conversations and turn basis:
+
+  ```
+  conversation-uuid
+  ├── turn-1
+  │   ├── stt_deepgramsttservice
+  │   ├── llm_openaillmservice
+  │   └── tts_cartesiattsservice
+  ...
+  └── turn-n
+      └── ...
+  ```
+
+  By default, Pipecat has implemented service decorators to trace execution of
+  STT, LLM, and TTS services. You can enable tracing by setting `enable_tracing`
+  to `True` in the PipelineTask.
+
+- Added `TurnTrackingObserver`, which tracks the start and end of a user/bot
+  turn pair and emits events `on_turn_started` and `on_turn_stopped`
+  corresponding to the start and end of a turn, respectively.
+
 - Allow passing observers to `run_test()` while running unit tests.
 
 ### Changed
@@ -23,6 +53,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `GoogleLLMService` has been updated to use `google-genai` instead of the
   deprecated `google-generativeai`.
 
+### Other
+
+- Added an `open-telemetry-tracing` example, showing how to setup tracing. The
+  example also includes Jaeger as an open source OpenTelemetry client to review
+  traces from the example runs.
+
+- Added foundational example `29-turn-tracking-observer.py` to show how to use
+  the `TurnTrackingObserver.
+
 ## [0.0.67] - 2025-05-07
 
 ### Added