Adjustable, draggable circles around markers in leaflet

I recently needed to implement a way of showing the uncertainty of a marker in a web map (the final application isn’t ready yet) and while I found a bunch of tutorials and stackoverflow answers that covered parts of this I couldn’t find a single page on how to do it. So I’m going to write it up here so that next time I need to do this a search will find this. TL;DR; You can see a simple demo here…