Save and load sfnetworks objects (using a format other than .RDS)

[agila5]

It might be nice to develop a write_sfnetwork and read_sfnetwork to save and write sfnetwork objects, possibly as a single .gpkg with two tables.

Check also what other people (tidygraph, OSMnx) are doing.

I vaguely remember that it was already mentioned, but I cannot find it now...

[tomalrussell]

As an example, over in nismod/snkit, we save out the nodes and edges GeoDataframes, typically to two layers in a GeoPackage, with default layer names nodes and edges:

https://github.com/nismod/snkit/blob/4ba9e6a8215b88c5146104f3643cedf4338d3e1f/src/snkit/network.py#L142-195