Update the tests to support nested dictionary request
Update the tests to support nested dictionary request

By default, the test APIclient uses 'multipart' as format which does
not support nested data.

This commits updates the settings to specify json as the default format.

vikoivun/kerrokantasi,stephawe/kerrokantasi,stephawe/kerrokantasi,City-of-Helsinki/kerrokantasi,stephawe/kerrokantasi,City-of-Helsinki/kerrokantasi,City-of-Helsinki/kerrokantasi,City-of-Helsinki/kerrokantasi,vikoivun/kerrokantasi,vikoivun/kerrokantasi