Changelog for the upcomming release (preview)

Changes

• Only Nextcloud 28 and up

Fixes

• Anonymize poll proposal owner in case of hidden results

What's Changed

🐛 Fixed bugs

• fix public registering by @dartcafe in #3189

Other Changes

• Code deduplication by @dartcafe in #3188

Full Changelog: v6.0.0-beta6...v6.0.0-beta7