I already saw that you have a support for OAuth Authentication but I can’t find nothing in the documentation regarding integrating en existing user base by specifying a custom /own IdP (Identity provider).
Our goal is enable seamless login experience to our existing users to a sore hosted by Shopify, so the OAuth Authentication is been forwarded to my own/ custom IdP.
Do you support such a scenario? Any information in this regard will be much appreciated.
Right now Shopify only supports SSO (with Multipass) for the Shopify Plus version. So if you are willing to go with the Plus version of Shopify this is the best option available.
You can also have alternate solution available which you can find here. I could integrate SSO with Custom Identity Provider with my Shopify store successfully.
miniOrange provides a SSO solutions for shopify Non-Plus and Plus versions. They provide Shopify SSO with any capable identity providers with different standard protocols included like OAuth,SAML,Open ID, JWT , Radius, WS-FED, etc.
They provided a suitable Single Sign-on (SSO) solution, so users never face a sign-on problem and also have a high level of security policy by configuring MFA . You can check out there Single Sign On - SSO Login App .