Ability to mark artificial segments to facilitate visualization & reconstruction of tiled geometry

[jerstlouis]

In relation to the clip-box query parameter investigated in the November 2021 code sprint alongside geometry simplification, it would be useful to be able to mark artificial segments introduced by clipping.
This avoids the need to request an extra boundary in order to keep the information about whether a particular segment is artificial.
It is also more difficult for applications wishing to reconstruct the geometry to use extra boundaries rather than explicitly marked artificial line segments, rather than the visualization use case where rendering to a smaller canvas will simply drop the oustide boundaries.

This was first proposed in Testbed 13 for GML, and an eventual solution for GeoJSON. We also implemented an approach to marking artificial segments in MapML for Testbed 15.

Our server currently optionally implements this as a property for GeoJSON output, e.g. the following sample generated by our server

         "line::hidden" : [
            { "polygon" : 1, "contour" : 0, "segments" : [ { "from" : 344, "to" : 345 } ] }
         ],

means that the edge from the 345th to 346th coordinates pair for the first contour of the second polygon is artificial.

JSON F&G could potentially define an extension with a dedicated property outside of GeoJSON properties to encode this information, in one way or another.

[cportele]

Meeting 2022-03-07: Discuss this in conjunction with #7.