Migrate to using json serialization library with null and type safety (built_value or json_serializer)

[OliverRhyme]

Feature Request

Use built_value or json_serializable library

Summary

Since the Dev and Socials models are increasing in complexity it is creating harder to maintain and less concise code. It is imperative to implement a json serialization, value type and enums type library. This shall remove a lot of boilerplate code and will also improve the type and null safeness.

Solution

Use built_value library since it already has the desired functionality.