Merge remote-tracking branch 'origin/REFACTORING_2021_05_20_START' into REFACTORING_2021_05_20_START

# Conflicts:
#	data
#	etc/requirements.txt
#	requirements/dev.in
#	requirements/dev.txt

Merge remote-tracking branch 'origin/REFACTORING_2021_05_20_START' into REFACTORING_2021_05_20_START

Merge remote-tracking branch 'origin/REFACTORING_2021_05_20_START' into REFACTORING_2021_05_20_START

Merge remote-tracking branch 'origin/REFACTORING_2021_05_20_START' into REFACTORING_2021_05_20_START

# Conflicts:
#	data
#	src/flask_covid19/blueprints/data_rki/rki_service_import.py