Azure AD / Entra ID setup
See complete documentation from Microsoft here:
https://learn.microsoft.com/en-us/entra/identity-platform/quickstart-register-app
register app as "Web app / api"
When done, send us application (client) ID, directory (tenant) ID and secret.
Then you will update the App with the ReturnURL we send you.
(and we need to know which client in your webshop this is for)