frames: add new StopFrame

src/pipecat/frames/frames.py

@@ -513,9 +513,9 @@ class CancelTaskFrame(SystemFrame):
 
 @dataclass
 class StopTaskFrame(SystemFrame):
-    """Indicates that a pipeline task should be stopped but that the pipeline
-    processors should be kept in a running state. This is normally queued from
-    the pipeline task.
+    """This is used to notify the pipeline task that it should be stopped as
+    soon as possible (flushing all the queued frames) but that the pipeline
+    processors should be kept in a running state.
 
     """
 
@@ -722,6 +722,17 @@ class EndFrame(ControlFrame):
     pass
 
 
+@dataclass
+class StopFrame(ControlFrame):
+    """Indicates that a pipeline should be stopped but that the pipeline
+    processors should be kept in a running state. This is normally queued from
+    the pipeline task.
+
+    """
+
+    pass
+
+
 @dataclass
 class LLMFullResponseStartFrame(ControlFrame):
     """Used to indicate the beginning of an LLM response. Following by one or