Migration requirements

This document has been split up. When upgrading openDesk, two types of migrations may be required:

• Manual checks and actions: See migrations-manual.md, which also holds the overview of the mandatory upgrade path and the deprecation warnings. It contains (at least) the details for the last two mandatory releases in the upgrade path, older upgrade instructions are archived in migrations-manual-archive.md.
• Automated migrations between versions, which openDesk runs on its own and which reduce the need for manual intervention: See migrations-automated.md, which also holds the catalogue of the available actions.