move migrators into oobmigration package
Created by: camdencheek
Importing internal/oobmigration into internal/database is problematic
from a cyclical import perspective. Since database
is imported all
over the codebase, we should keep the import footprint of that package
as small as possible. This moves internal/database/oob_migration.go to
internal/oobmigraiton/migrators.go to avoid this issue.