We have a solar design tool and proposal quoting webApp i.e. users can design their solar roof design and create a proposal. As a first step, we would like to allow Shopify User to use their ShopifyID, be redirected to our website, and get logged in (SSO, OAuth, etc.) seamlessly.
Second, once they have designed, quoted, and signed the contract - the order should be placed back to the storefront based on the BOM and SKU that the design tool will generate/map.
I believe the second step can be achieved using the storefront API to actually place the order. The question is pertaining to the first - how do I uniquely identify the ShopifyID user uniquely into our WebApp and more importantly seamless log them in.
And yes we are using Shopify Plus.
For the first step, Plus merchants get access to Multipass login which sounds like something you could use to accomplish that, provided the users log into your external service first.
For the second step, the Orders API under the Admin API can be used to create either draft orders (GQL/REST versions) or a regular order with the information you desire. You could use the storefront API's checkoutCreate if you're considering a headless solution.
Hope that helps!
Sorry for misinterpreting there, I don't think there's a clean way to support that use case.
As i can understand you want the same user who is logged in to your shopify store to be direclty logged in to your external website. If that's the case, i think that is possible. I would require more information regarding your external website so that i can help you with your problem. I'm sending you my email address in personal message to continue this discussion over email.