Execute custom SQL script as part of Entity Framework migration

I have been using the standard add-migration approach to updating my aspnet core database on Entity Framework. I now have to move two "image" columns into a new table (and their image data), remove the columns from the original table, and set up a foreign key relationship between the old and new tables. I have a working SQL script to do all this.

How can I execute this sql script as part of a normal EF migration, AND make sure subsequent add-migration changes will reflect the changes that my sql script will do (adding new table/columns, removing image columns from original table)?

I've seen a few references to SqlFile and deriving from DbMigration, but nothing that fits my scenario nicely. I am using EF Core, aspnet core 2.0.