Create flow chart of areas that touch Authentication

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### What is this about?

To better understand how to consolidate auth logic, we need to consider all of the areas that touch and utilize auth business logic. Visually representing these flows and commenting the moving parts beside them will paint a clear picture of what needs to be updated. Some of the things to consider and record while performing this task:
- What are the states that are being tracked? Ex. `existingUser`
- Do you see any shared logic between the flows?
- Does the auth logic need to live in that flow or can it be moved to a more reliable area?

Recommendation - Use Figma flowchart to create the flow - https://www.figma.com/templates/flowchart-maker/

### Scenario

_No response_

### Design

_No response_

### Technical Details

- Use Figma flowchart to create a flow chart of flows that utilize auth logic - https://www.figma.com/templates/flowchart-maker/
- When taking notes in the chart
- What are the states that are being tracked? Ex. `existingUser`
- Do you see any shared logic between the flows?
- Does the auth logic need to live in that flow or can it be moved to a more reliable area?

### Threat Modeling Framework

_No response_

### Acceptance Criteria

- Flowchart for auth flows are visualized in Figma
- Flowchart includes notes pointing out states that are being tracked as well as common business logic

### Stakeholder review needed before the work gets merged

- [ ] Engineering (needed in most cases)
- [ ] Design
- [ ] Product
- [ ] QA (automation tests are required to pass before merging PRs but not all changes are covered by automation tests - please review if QA is needed beyond automation tests)
- [ ] Security
- [ ] Legal
- [ ] Marketing
- [ ] Management (please specify)
- [ ] Other (please specify)

### References

_No response_

No files, tests, or entry points are named, so begin by tracing the authentication flows and shared business logic in the repository. Record tracked states, shared logic, and possible consolidation points in a Figma flowchart; done means the auth flows are visualized with those notes included.

Written by the indexing model from the issue text.