Add patch activation callback

CHANGELOG.md

@@ -22,6 +22,7 @@ to docs, or any other relevant information.
 ### Added
 
 - Exposed `Temporalio::Workflow::ContinueAsNewError#backoff_start_interval`, to allow the new workflow to start after a delay.
+- Added the experimental `Temporalio::Worker` `patch_activation_callback:` option, allowing workers to decide whether a first non-replay `Temporalio::Workflow.patched` call should activate a patch during rolling deployments.
 
 ### Fixed
 
@@ -81,4 +82,3 @@ correctly receives `Temporalio::Error::WorkflowUpdateFailedError`. (#454)
 but defers dispatch to a worker until the delay elapses. Retry attempts do not re-apply the delay.
 `ScheduleToStart` and `ScheduleToClose` timeout clocks begin counting after the delay
 elapses; `StartToClose` and `Heartbeat` are unaffected. Currently experimental.
-

README.md

@@ -660,7 +660,8 @@ from workflows including:
 * `all_handlers_finished?` - Returns true when all signal and update handlers are done. Useful as
   `Temporalio::Workflow.wait_condition { Temporalio::Workflow.all_handlers_finished? }` for making sure not to return
   from the primary workflow method until all handlers are done.
-* `patched` and `deprecate_patch` - Support for patch-based versioning inside the workflow.
+* `patched` and `deprecate_patch` - Support for patch-based versioning inside the workflow. Workers can set
+  `patch_activation_callback:` to decide whether a newly introduced patch should activate during rolling deployments.
 * `continue_as_new_suggested` - Returns true when the server recommends performing a continue as new.
 * `current_update_info` - Returns `Temporalio::Workflow::UpdateInfo` if the current code is inside an update, or nil
   otherwise.