* refactor volvooncall to use ConfigFlow
* remove unused constant SIGNAL_STATE_UPDATED
* implemented feedback
* improve ConfigFlow UX by giving an option for region=None
* implemented more feedback
* next round of feedback
* implemented more feedback
* improve test coverage
* more test coverage
* Apply suggestions from code review
* implemented feedback on tests
* Apply suggestions from code review
Co-authored-by: Martin Hjelmare <marhje52@gmail.com>
