How to Implement a Secure Central Authentication Service in Six Steps - Shopify

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This post details the six-step process for implementing Shopify's central authentication service, Identity. It covers synchronizing user data from existing accounts, routing all authentication through OIDC, prompting users to combine legacy accounts into a single Identity account, encouraging 2FA adoption, creating the combined Identity account within a database transaction, and preventing the creation of new legacy accounts. It also explains the modeling of Identity and Legacy accounts, the MergeSession object for account combining, and the handling of 2FA requirements during the merge process.