Confirm shop ownership

[hpatoio]

I've a Sass and I need to connect a user with his/her Shopify's shops. I've create a form where the user can add the domains of the shops he/she own.

Everything works but the questions is: how do I validate that he is the real owner ? I was thinking about an approach like the one used by Google Analytics: ask the user to upload a file with a specific name/content on his shop but I was just wondering if there is an easier/faster way.

Thanks

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Simone