[enhancement]: Implement phase 5 of the multiuser implementation plan

[lstein]

Is there an existing issue for this?

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Contact Details

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What should this feature add?

Implement phase 5 of the multiuser implementation plan at docs/multiuser/implementation_plan.md. See also docs/multiuser/specification.md. Provide automated and manual testing instructions.

Base the work on the default branch lstein-master.

Alternatives

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Additional Content

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