[EPIC] LTI 1.3 integration #2613

Context

As proposed in #2432, we are exploring launching Docs directly from a Learning Management System (LMS) via the LTI 1.3 standard. In LTI terms, the LMS is the Platform and Docs is the Tool.

This is a meta issue: it should hold the scope, the design decisions and the current state of the work. Implementation will happen in sub-issues that will be linked here. Task-specific discussions should then take place in the corresponding sub-issues.

Goals

• A teacher can add a Docs activity to a course; learners click it and land in the document, already authenticated, with the right permissions.
• No separate account creation and no second login step.
• Works with any LTI 1.3 certified LMS (e.g. Moodle, Stud.IP) — no LMS-specific code.

Target scenarios

1. Shared course doc — one document per activity, all enrolled learners can edit collaboratively
2. Handout — one document, instructors edit, learners read
3. Per-learner doc — each learner gets their own document, instructors can read all of them
4. Deep linking — the instructor picks or creates the document from the LMS content picker

Open questions

1. Identity: Ideally accounts in LTI can map to accounts from single-sign-on system like keycloak.
2. Ownership: Who owns a document created through a launch — the instructor, or the instance? What happens when the instructor leaves? It would be good to have a admin account that owns all documents created via LTI.
3. Lifecycle: Does the document outlive the course? Can learners still reach it after the course ends? Data retention expectations differ per institution.
4. Role mapping: how do LTI roles map to roles/rights in Docs?