Check and convert origin and destination inputs
assign_points_input(df, name)A data.frame with columns id, lon and lat.
Either a data.frame or a POINT sf.
Object name.
Other assigning functions: 
assign_decay_function(),
assign_departure(),
assign_drop_geometry(),
assign_max_street_time(),
assign_max_trip_duration(),
assign_mode(),
assign_opportunities(),
assign_osm_link_ids(),
assign_shortest_path()