AddColumn extensions for EFCore migrations #1527
Description
Today we have database agnostic extensions (supporting the types we have support for) that lets you define columns when we create an initial table migration.
We need to have the same for adding columns, so think AddStringColumn(), AddGuidColumn() and so forth.
Today we have ColumnExtensions. We could then have AddColumnExtensions. However, it would be great if they share the same way of creating the AddColumnOperation. Not sure if EFCore allows us to just add a AddColumnOperation directly. If it does, we should just leverage existing extension methods, or create something that both use. Whatever is the easiest.