Propagate type arguments

[WoH]

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• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you written unit tests?
• Have you written unit tests that cover the negative cases (i.e.: if bad data is submitted, does the library respond properly)?
• This PR is associated with an existing issue?

Closing issues

• closes Swagger not showing intersection model properly #391
• closes Support generic type parameter and return type #27

If this is a new feature submission:

• Has the issue had a maintainer respond to the issue and clarify that the feature is something that aligns with the goals and philosophy of the project?

Please comment if handling Models with multiple type parameters is not something you want to support and I'll throw on that :)

Potential Problems With The Approach

This PR assumes the scope of the type arguments has been checked by typescript (which is reasonable I think).

Edit: I don't like the implementation, but it's a lot less bad :/

Test plan

I'm sure there are millions of possible scenarios we want to spec here, I have no clue what to cover yet, I intend to keep this a draft until this section is less depressing to read.

[dgreene1]

Looks good to me @WoH. I think the only thing that's confusing is that I can't find the line where this.context is set for the first time.

As far as tests cases go, I'm fine if we just copy the examples from the two issues you referenced.

[ryankeener]

@WoH this fixes the issue I was seeing, thanks!

@dgreene1 it's getting initialized in the constructor, no?

[dgreene1]

I see that it's initialized in the constructor but I was wondering if the consuming module sends in the context. I don’t think it does. I think it's the TypeResolver itself when it constructs another TypeResolver.