Prepare for Django 4.0

• Use scrypt password hasher
• Use native Redis cache backend
• Use FormMixin API of DeleteView (@hansegucker, please check: https://docs.djangoproject.com/en/dev/releases/4.0/#deleteview-changes)
• Suppot settingtrusted origins (drive-by fixing missing feature)
• Remove leading / from STATIC_URL (drive-by fix)
• Remove USE_L10N and USE_I18N from settings as they now default to True

added part::backend type::feature type::refactoring labels

assigned to @hansegucker

created merge request !808 (merged) to address this issue

mentioned in merge request !808 (merged)

marked the checklist item Use FormMixin API of DeleteView (@hansegucker, please check: https://docs.djangoproject.com/en/dev/releases/4.0/#deleteview-changes) as completed

assigned to @nik and unassigned @hansegucker

closed with merge request !808 (merged)

mentioned in commit 092963f4