`is_valid` for all geometry types. about geo HOT 3 OPEN

Some time ago I tried to implement various validity checks for geo-types geometries : https://github.com/mthh/geo-validity-check

I think it implements most of the validity checks of GEOS as well as some other checks.

The non-validity diagnostic messages could greatly be improved, and there is no functionality to attempt to repair the geometries.
Anyway, if that would be useful, feel free to reuse code from this crate to implement an is_valid function directly in geo.

from geo.

For LineString, its requirements are either empty, or 2+ coordinates. This is trivial to check. In addition, if the LineString is closed, it must also not self-intersect. We can check this by using Intersections (inserting all the edges in the line string) and checking that all intersections are vertices of the original line string (it's not clear to me if a line string is allowed to use the same vertex twice, but if it's not then I think we can just check if there are any intersections).

from geo.

Somewhat related to #1120

from geo.