Plumbing an Ice Machine Drain

Hello. My church recently purchased an air-cooled under-the-counter Manitowoc ice machine. In the cabinet slot where it is going to be installed (on the far end of the kitchen with its back against an exterior wall consisting of sheet rock/insulation/metal siding), we do have a water hookup available but do not have any drain to accommodate the gravity drain on the back of the machine (for ice melting in the storage bin).

We have thought about just piping a drain out the wall to the exterior of the church since it would be on the back side of the building. However, I don’t really know the best way to do that. We would also like it to be where we could slide the machine out from the wall if needed for maintenance, etc. Also, we don’t want bugs or other creatures getting in through the pipe. Is an air gap needed in the drainage? Any advice would be appreciated. Thank you.