MBRTouches(g1, g2)

Two geometries spatially touch if their interiors do not intersect, but
the boundary of one of the geometries intersects either the boundary or
the interior of the other.

This function returns 1 or 0 to indicate whether the minimum bounding
rectangles of the two geometries g1 and g2 touch.

MBRTouches() handles its arguments as described in the introduction to
this section.

URL: https://dev.mysql.com/doc/refman/8.4/en/spatial-relation-functions-mbr.html

