Background

We use OneFlow successfully for our apps for quite some time.
It is about time to use OneFlow for core as well!

Steps to take

• move current master branch to archive/master - just for the sake of not loosing anything
• move stable10 to master - this will be our main branch to release any future ownCloud 10.x.x
• review all drone and remaining travis configurations and test with daily-master-qa only - done by @phil-davis 2019-08-01
• transifex will operate on master
• update nightly scripts to build only nightly for master ( which is then stable10 ) - https://github.com/owncloud/administration-internal/pull/149
• build only containers for nightly master
• smashbox && update-testing only for master
• app acceptance tests no longer against core stable10 - just against "new" core master and latest core release (see long list of linked PRs below)
• keep user_management in core for now - app can be split again later - if necessary
• remove encryption app - Remove encryption app #35949

Benefits

• no waste of time with backporting master -> stable10
• no more translation backports
• far less jobs on drone