plan/policy.go
func (p *UpsertOnlyPolicy) Apply(changes *Changes) *Changes {
	return &Changes{
		Create:    changes.Create,
		UpdateOld: changes.UpdateOld,
		UpdateNew: changes.UpdateNew,
	}
}
func (p *UpsertOnlyPolicy) Apply(changes *Changes) *Changes {
	return &Changes{
		Create:    changes.Create,
		UpdateOld: changes.UpdateOld,
		UpdateNew: changes.UpdateNew,
	}
}
// Apply applies the upsert-only policy which strips out any deletions.