Best way to sell insurances associated to products

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I have a shop that sells phones, now we need to include a product that consists in a insurance fot that phone. 

The insurance one time the phone and the insurance will sold, this will be created via API to extern provided with data of the customer.

I would to talk about the best strategy to do this:

1- Insurance are independents products, the problem here is to relation the phone sold with the insurance.

2- Insurance is a product attribute, one time the order will be created, the API of the insurance will be fired and other data will be saved in custom tables.

Thank you. Regards.

[templaries]

Any ideas of this. Thank you,