Support for Custom Client Identity on Schedule Trigger

[deepika-awasthi]

Is your feature request related to a problem? Please describe. We’re trying to differentiate between workflows triggered automatically by a schedule and those triggered manually—such as via the Temporal UI, API, or dashboard. While the TemporalScheduledStartTime search attribute helps in distinguishing scheduled runs in some scenarios, there’s currently no way to identify who or what initiated a manual trigger (e.g., via ScheduleHandle.trigger() or the UI). Additionally, interceptors like ScheduleClientCallsInterceptor.CreateScheduleInput don’t provide enough context to determine the trigger source.

Describe the solution you'd like We’d like a metadata field—such as trigger_source or client_identity—to be added to the schedule trigger context. This would allow us to track whether a manual trigger came from the UI, a specific service, or another user.

Describe alternatives you've considered As a workaround, we plan to compare nextActionTime with the actual workflow start time and then manually set a trigger_type search attribute within the workflow.

Additional context Related Slack discussion: https://temporaltechnologies.slack.com/archives/C076CB0E075/p1747790772423569