Swiss profiles return ellipsoidal distances, QGIS profiles use cartesian ones

[gacarrillor]

For reference, see QGIS issue and another related plugin issue.

This is the result of a Swiss profile when using a QGIS project in EPSG:3837 (I'm measuring the profile line on the main QGIS canvas in both ellipsoidal and cartesian modes):

Approximately the same profile when using a QGIS project in EPSG:2056 (which is the EPSG requested by the Profile API):

Measurements for EPSG:2056, in both ellipsoidal and cartesian modes are almost the same, the difference is a matter of millimeters.

[gacarrillor]

A possible solution to avoid tweaking QGIS code would be to calculate our own (cartesian) distances and only use heights from the profile API (ignoring the distances it returns). This depends on the QGIS-CH requirements.