Refactor TOTP adaper to return strings

[dblythy]

New Feature / Enhancement Checklist

• I am not disclosing a vulnerability.
• I am not just asking a question.
• I have searched through existing issues.

Current Limitation

As discussed in #8457, mixed return types for the TOTP adapter makes it incompatible with certain client SDKs

Feature / Enhancement Description

Refactor adapter to return strings

Example Use Case

Alternatives / Workarounds

3rd Party References

[parse-github-assistant]

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[parseplatformorg]

🎉 This change has been released in version 6.3.0-alpha.6

[parseplatformorg]

🎉 This change has been released in version 6.4.0-beta.1

[parseplatformorg]

🎉 This change has been released in version 6.4.0-alpha.1

[parseplatformorg]

🎉 This change has been released in version 6.4.0