Update docs with a reminder about writing safer migrations (#10809)
Update docs with a reminder about writing safer migrations (#10809)

* Update docs with a reminder about writing safer migrations

* Updates following code review - renaming columns needs three steps
flodolo/bedrock,alexgibson/bedrock,alexgibson/bedrock,mozilla/bedrock,sylvestre/bedrock,flodolo/bedrock,pascalchevrel/bedrock,craigcook/bedrock,alexgibson/bedrock,pascalchevrel/bedrock,sylvestre/bedrock,craigcook/bedrock,craigcook/bedrock,craigcook/bedrock,flodolo/bedrock,mozilla/bedrock,flodolo/bedrock,mozilla/bedrock,mozilla/bedrock,pascalchevrel/bedrock,alexgibson/bedrock,sylvestre/bedrock,pascalchevrel/bedrock,sylvestre/bedrock