Increase hashing capabilities from SHA1(vulnerable) to SHA256 or higher

### Is your feature request related to a problem? Please describe.

It has been made clear by the industry at IBM that SHA1 is suspect in its partial security weaknesses and causes applications that use the box sdk to fail app scan testing as the box sdk is not secure enough and needs safer hashes.
### Describe the solution you'd like

Box needs to add SHA256 and SHA512 compatibility so the sdk can be classified as safe and not cause vulnerabilities for companies such as IBM that use the sdk
### Describe alternatives you've considered

No clear alternative yet as my entire application works on the box sdk
### Additional context

This is a high priority item and should be remedied as soon as possible to make the box sdk secure again