Expand fragment input definition parser to work with nested types

[DeamonDev]

💥 Proposal

Currently the FragmentParameterTypingParser used for parsing fragment input definitions works only for types of depth at most one. By that I mean the naturally associated AST tree for the type definition has height at most one. I propose to expand this parser to work with arbitrary definitions. So for examply it will be able to parse types such as:

• Map[List[String], Map[String, Float]] (depth = 2)
• Map[String, Map[String, Map[String, Map[String, Float]]]] (depth = 4)