Descriptors

Part of the goal of using dedicated AutoflexField definitions is that we can compile this data into a nice way to visualise it both in the terminal and on the web. It can be used as a more helpful visualisation tool than the standard type descriptions.

We want to provide the implementation of the Field functionality so that an AutoflexField compiles into a standard Pydantic Field whilst using the json_schema_extra to encode the information accordingly.