backend part of the new traffic volume page

compendium_v2/background_task/parse_excel_data.py

compendium_v2/db/model.py

...rations/versions/3730c7f1ea1b_add_traffic_volume_table.py

compendium_v2/publishers/survey_publisher_v1.py

compendium_v2/routes/api.py

compendium_v2/routes/traffic.py

test/conftest.py

test/test_traffic.py