BREAKING CHANGE: update registry version: Updated the encoding scheme to base64 to the `lookup/shells?assetIds...` in dpp-backend

[saudkhan116]

This PR contains the following changes:

• Updated digital twin registry version to from 0.3.15-M1 to 0.3.31.
• Encoded assetIds into base64 in the dpp-backend

What we want to achieve with this PR?

Updated the dpp-backend to support the digital twin registry version 0.3.31

What is new?

Updated

• Updated the encoding scheme to base64 to the lookup/shells?assetIds... in dpp-backend
• Updated the digital twin registry version to v0.3.31