StartWorkflow Rejects Valid Link.NexusOperation Variant

[VegetarianOrc]

Expected Behavior

When sending links to be associated with a workflow, NexusOperation links are accepted.

Actual Behavior

NexusOperation links are rejected as an unsupported variant.

Steps to Reproduce the Problem

1. Send a StartWorkflowExecutionRequest where the Links field contains a valid Link.NexusOperation variant.
2. Observe the unsupported variant rejection from the server.