Update duo workflow doc with latest client doc

Frédéric Capletterequested to merge
fc-update-flow-doc into main

Why is this change being made?

This merge request updates the documentation for GitLab's Duo Workflow feature to reflect recent architectural improvements. The main changes include:

UI Architecture Updates: The documentation now explains how the user interface is being restructured to share common components between the web version and IDE extensions. Instead of building separate interfaces, they're creating reusable building blocks that work across different platforms while keeping platform-specific logic separate.

API Improvements: The system is moving away from exposing raw internal data (called "checkpoints") to clients, which was causing performance issues and making it difficult for developers to work with. They're replacing this with a cleaner, more efficient API called "duo_messages" that only sends the data that user interfaces actually need.

Real-time Updates: The documentation clarifies how the interface receives live updates as workflows progress, switching from one technology (GraphQL subscriptions) to another (websockets) for better performance.

State Management: The docs better explain how the system handles different workflow states and user interactions, particularly when workflows need to pause and wait for user input.

The changes also add a new architectural decision record that formally documents why they're deprecating the old checkpoint system in favor of the new duo_messages approach, citing developer experience and performance benefits.

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Commits

  • Update duo workflow doc with latest client doc

There was a lot of old documentation around the client behaviour so we update it. Also adding a decision log for deprecating the checkpoint field.

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