Little worried I might have cut too much, but there was so much detail in this thing that just made it actually kind of unusable. Trying to find the right balance of information for context and actions to take to do the migration work.
- De-duplicates bulk of the content for a migration from v4 to v5
- Adds clear breaking labels where appropriate
- Leaves room for more guidance around doing the actual migration
/cc @XhmikosR