Optimize auth.js: Replace Buffer.byteLength(body).toString() with simple body.length

[studentIvan]

Summary

Replace Buffer.byteLength(body).toString() with simple body.length. It allows to use only Buffer.from polyfill, instead of the entire Buffer's polyfill (around 50kb)

Description

Check the sdk-auth umd file - we see the entire Buffer's polyfill here. For what?

Todo

• Tests
  • [ ] Unit
  • [ ] Integration
  • [ ] Acceptance
• [ ] Documentation
• [ ] Type label for the PR