If you're looking to authenticate a customer in a third party system you'll need to look into using the Multipass API. Do note that this API is scoped to Shopify Plus merchants only so not all shops will be able to access it.
We are looking into implementing login in our app via Shopify, which would ideally serve as OIDC, since it supports Oauth protocol.
However I saw that Oauth is supported for apps, but I found no info on how that would work for external users.
Any help is much appreciated.
Did you find a way to do this?
Also want to know the process for having customers use Shopify as Identity Provider for an external platform, vs having a separate login for the platform.