* Add time_deregistration_end field to events resource

* Fix flake8 issues

* Update amivapi/tests/fixtures.py

Co-authored-by: Dominique Portenier <75583205+d-portenier@users.noreply.github.com>

* Adjust fixture based on review

* Fix tests

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Co-authored-by: Dominique Portenier <75583205+d-portenier@users.noreply.github.com>