Port the Geometry Snapper plugin to processing
Snap geometries algorithm allows snapping
to other layer types, supports point/line layers
Snap to layer algorithm accepts a mode parameter. With a new option to prefer to snap to closest point on geometry.
The old behaviour was to prefer to snap to nodes, even if a node
was further from the input geometry than a segment. The new option
allows you to snap geometries to the closest point, regardless
of whether it's a node or segment.