refactor(auth): email mfa optimizations

[jjarvisp]

Description of changes

The purpose of this pull request is to address feedback, optimize, and refactor previous email mfa updates.

Issue #, if available

Description of how you validated changes

• unit tests
• manual testing

Checklist

• PR description included
• yarn test passes
• Unit Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)

Checklist for repo maintainers

• Verify E2E tests for existing workflows are working as expected or add E2E tests for newly added workflows
• New source file paths included in this PR have been added to CODEOWNERS, if appropriate

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.