[Brook] Added the Activity and client stream handles over Core.

changelog/added/pirouetting-platypus.md

@@ -0,0 +1 @@
+Add experimental `temporalio.contrib.streams` so a Workflow can publish ordered records to a Redis stream with its Workflow Task, and Activities and clients can read them.

temporalio/contrib/streams/__init__.py

@@ -37,6 +37,13 @@
 context then reaches a stream the same way:
 
 - Workflow code publishes to its own stream with :func:`workflow_writer`.
+- An Activity reaches the stream of the Workflow that scheduled it with
+  :func:`activity_handle`, and writes as itself: its Activity id with the
+  scheduling run id, and its Temporal attempt. The handle is pinned to that
+  run, so a read on it ends when the run closes, Continue-as-New included.
+- Any process holding a client reaches a Workflow's stream with
+  :func:`get_stream_handle`, and writes with a producer id and an attempt of
+  its own.
 
 The stored record is ``temporal.sdk.streams.v1.StreamRecord``, in
 :mod:`temporalio.bridge.proto.streams.v1`, with the user's value in ``body``
@@ -57,6 +64,13 @@
     StreamStorageError,
     StreamUnsupportedError,
 )
+from temporalio.contrib.streams._handles import (
+    ActivityStreamHandle,
+    StreamHandle,
+    StreamProducer,
+    activity_handle,
+    get_stream_handle,
+)
 from temporalio.contrib.streams._plugin import StreamStorePlugin
 from temporalio.contrib.streams._record import (
     Cursor,
@@ -69,6 +83,7 @@
 from temporalio.contrib.streams._workflow import WorkflowStreamWriter, workflow_writer
 
 __all__ = [
+    "ActivityStreamHandle",
     "BEGINNING",
     "Cursor",
     "DEFAULT_TOPIC",
@@ -78,9 +93,11 @@
     "StreamCursorError",
     "StreamError",
     "StreamExpiredError",
+    "StreamHandle",
     "StreamNotFoundError",
     "StreamOutcomeUnknownError",
     "StreamOwnerKind",
+    "StreamProducer",
     "StreamProducerError",
     "StreamRecord",
     "StreamRecordError",
@@ -92,6 +109,8 @@
     "StreamUnsupportedError",
     "Supersession",
     "WorkflowStreamWriter",
+    "activity_handle",
+    "get_stream_handle",
     "topic",
     "workflow_writer",
 ]