If we go for option #2, we will lose all our existing data; however, it will be recreated by the DbSeeder at the first run, so we'll only lose what we did during our CRUD-based tests during the last three chapters.
Although it might seem a horrible way to fix things, that's definitely not the case; we're still in the development phase, hence we can definitely allow a full database refresh.
Should we choose to take this bus, here are the commands to use:
dotnet ef database drop dotnet ef database update
The drop command should ask for a Y/N confirmation before proceeding; when it does, hit the y key and let it happen. When the drop and the update tasks are both done, we can run our project in debug mode and wait for the DbSeeder to kick in and do its magic; once done, we should have an updated database with .NET Core Identity support.