Need to build model in ehighways resolution

[jnnr]

• First, build spatial units for ehighways (see some comments in Build ehighways resolution units #318).
• Point to ehighways potentials: https://zenodo.org/records/6600619. This repo contains potentials for all resolutions, regional, national, continental, ehighways (It should also contain the polygons of the eligible areas)
• add another case to if-else-statement in

  euro-calliope/scripts/transport/aggregate_timeseries.py

  Line 71 in 6a58b33

  if resolution == "continental":

[timtroendle]

This has been implement in #370.