MMU Slot buffer - Slot for PC4_M10 - with threads and recessed handle

This is a remix of the PC4_M10 slot for the original MMU Slot buffer.  It contains two models.  The first solely includes a recess where the handle attaches to the slot.  The benefit is that the original handle can be used and the “fingers” of the handle do not extend beyond the slot.  That should minimize any rubbing of  the filament on the handle.

It also includes a version that has M10x1 threads in the model for easier attachment of the PC4_M10 fitting.  However that version very likely requires supports.  In my testing printing PETG on a Prusa mk3s+, I set the support overhang threshold to 29° and it only produced supports under the threads.  The supports themselves came away very cleanly and the PTFE fittings screwed in quite easily.

I've printed successfully with PETG and a .4mm nozzle with .2mm layer height and 15% infill.