Support using query string parameters on JSON-mapped columns

[bkoelman]

Entity Framework Core 8 adds improved support for filtering, sorting, and projecting JSON-mapped columns. And PostgreSQL support has been implemented since v8.

This issue tracks the work for implementing similar support for JSON:API. It would potentially enable filters such as /users?filter(equals(address.country,'Netherlands')) where Address is stored as a keyless JSON object in the Users table.