Creates a Xero contact via Nexus using the partner or MVNO legal entity as the source of truth (company name, registration number, contact email). Requires an entity to be linked, but does not require the full FICA review to be complete. No request body: business data is never re-collected from the client.

Access: Auth methods: JWT bearer. Requires any permission: partner:admin, partner:finance, finance-report:read, finance-order:write. Partner scope: partnerId from query.