Prepare v2.4.10-rc.1

Tasks to be done BEFORE releasing

• CHANGELOG: grab all merge request that were merged since previous release, select the most interesting ones and quickly describe them according to KeepAChangelog.com
• CODE: change the version in config/bootstrap.php
• DOC: create the upgrade doc in Documentation/For_ops/UPGRADE
• CHANGELOG: as a final step, set the date of the release