Shared data schema for backend and frontend

[codemonkey800]

We should define the data types shared between the backend and frontend in a shared schema file so that changes to the underlying data model are propogated to the other codebases.

Some options:

• JSON schema
  • We already use JSON for the APIs, so would be easier to integrate
  • Use generators for TypeScript types
• Protobuf
  • Binary data format, so slightly more efficient (but maybe not necessary)
  • Can generate type definitions and mode classes for TypeScript and JavaScript

[manasaV3]

Adding graphql to the mix of options.