Terrain profile along a straight line (at most 2000 m)

Samples dhm_terraen every trin metres from fra to til, ALWAYS including both endpoints, and reports fald_m (the fall across the line). One upstream raster, not one per station. Consumes ONE billable unit per returned station. The answer carries the fall and nothing more — whether a project clears the højdegrænseplan is not this API's call. The line may be at most 2000 m long (measured in EPSG:25832) and yield at most 500 stations; a longer line or a finer trin is REFUSED with a 400 naming the limit. Lines over ~240 m are read from a coarser raster than the native 0.4 m — oploesning_m states which. A station outside the model's coverage (abroad, open sea) is terraen_m: null, never 0.