[VBLOCKS-1910] Platform tokens

[mhuynh5757]

Submission Checklist

• [ ] The CHANGELOG.md reflects any feature, bug fixes, or known issues made in the source code
• [x] New unit tests and integration tests have beed added
• [x] Code coverage is more or equal to the previous coverage
• [x] A visual inspection of the Files changed tab was made prior to submitting the pull request ensuring the style guide was followed
• [ ] CI pipeline is green
• [x] ~Included screenshot if necessary~

Description

This PR fixes the token vending mechanism to recognize the platform the token is being vended for, and adjust the incomingAllow and pushCredentialSid properties appropriately.

Breakdown

• Include platform in client-side fetch.
• Parse platform on server.
• Tests for client and server.

Validation

• Tests and manual validation on emulator.

Additional Notes

N/A

Contributing to Twilio

All third-party contributors acknowledge that any contributions they provide will be made under the same open-source license that the open-source project is provided under.

• [x] I acknowledge that all my contributions will be made under the project's license.