Self-Service Ordering Tip Function

[#1]

We are excited to use the self-service ordering feature for a theatre, allowing patrons to order directly to their tables and seats.  While pickup & delivery options feature a tip function, the self-service ordering option doesn't seem to include a tip option. Since we'll have to hire runners to get the orders to patrons, we'll need the tip option for the self-service ordering to make sense for us.