Create a single credentialing workflow for a practitioner

Creates a new credentialing workflow for a practitioner and returns the created object with a server-assigned id and initial status. Use this endpoint for single-practitioner workflow creation; use POST /credentialing-workflows/bulk-create or POST /credentialing-workflows/v2/bulk-create for batch operations. The practitioner identified in the request body must already exist in the system. Returns 409 if an active workflow already exists for the same practitioner and tenant.