Add $ref resolution to JSON schemas

[naz]

Problem

admin-api-schema's get() method returns raw json schemas without resolving definitions used in $ref. This makes get method hardly usable if somebody needs to see whole schema (for example when used in documentation). More on this read this comment.

Solution

One of possible solutions could be adding $ref resolution through package like ref-parser. But more research should be done into use-cases and other solutions first