Allow External Libraries to add functionality to Cypher Generation

[adam8797]

Ok Ok, before you freak out at how big this change could be, I mostly want this to track work. If I've got time, I'd like to contribute to this solution, but I figure as an expert on the library you might have some input.

Right now I maintain a few extensions in a library I call Neo4jClient.ReturnPoly that essentially allow you to setup a type hierarchy in c# and then reflect that in Nodes and Tags.

And so far its worked great without any modifications to the base library, just a handful of extensions and JsonConverters.

However, I've recently been working on doing this conversion in Anonymous or built types (.Return(() => new { ... }) ) and I've run into a bit of a snag. I've found a way to do it, but it requires end users to go and use Return.As<T>(string) and chain it with a static method: .Return(() => new { Data = Return.As<MyType>(PolyUtils.Poly("n")) }); which is just a little too verbose.

I'd like to see a way where I can kind of hook into the Cypher Generation code, or provide a type that it knows how to convert.

What I would like to be able to do is .Return(n => new { Data = n.AsPoly<MyType>() }) where I would provide the AsPoly method in an external library, then the cypher generation would also just hook my library for the actual implementation.