Feature/exceptional situations add municipality

[juuso-j]

Exceptional situation add municipality

Trello #603

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Breakdown:

Model

1. exceptional_situations/migrations/0003_situationannouncement_municipalities.py
2. exceptional_situations/models.py
   • Add M2M field municipalities

API

1. exceptional_situations/api/serializers.py
   Serializer municipalities
2. exceptional_situations/api/views.py
   • Filter municipalities

Importer

1. exceptional_situations/management/commands/import_traffic_situations.py
   • Import municipalities

Tests

1. exceptional_situations/tests/conftest.py
   • Add municipalities
2. exceptional_situations/tests/test_api.py
   • Test municipalities filter
3. exceptional_situations/tests/test_import_traffic_situations.py
   • Test municipalities import