Currently fdm-core expects WKT as input and returns WKT as output for geometry columns. However, at fdm-app we need for various dependencies to use GeoJSON. This is fine a as we can convert with the wkx library between WKT/WKB and GeoJSON. But the wkx library is currentely not updated anymore and becomes outdated as it cannot be used at the browser and causes some warningst at building the package. Also at #75 an bug is introduced that has somewhat to do with the internals at wkx.
To simplify things, I would propose to drop wkx as a dependency and use from now on GeoJSON as format to communicate about geometries