Migrating to DefineMap

A training series on migrating to 3.0 app that follows the same flow as the migration guides.

Personally, I'd like more time spent on using DefineMap and view callbacks but we can make those separate training videos on using those specific modules.

Start by reviewing the migration guides and the proposed training flow for migrating to the 3.0 app. Clarify how DefineMap and view callbacks should be covered, then create the training series so it follows the migration-guide flow and clearly separates those module-specific topics into possible additional videos.

Written by the indexing model from the issue text.