Use JSON.mapping for Generators

[bmulvihill]

I believe we should be using JSON.mapping to simplify our Generator classes and make the code a bit cleaner. We can simply map the canonical_data.json and create our Generator/Test Cases.

Example:

class HelloWorldGenerator < ExerciseGenerator
  JSON.mapping(
    exercise: String,
    version: String,
    cases: Array(HelloWorldTestCase)
  )
end


class HelloWorldTestCase < ExerciseTestCase
  JSON.mapping(
    description: String,
    property: String,
    expected: String
  )

  def workload
    "HelloWorld.hello.should eq(\"#{expected}\")"
  end

  def test_name
    description
  end
end

[mhelmetag]

I saw that in the last PR you made. I think that makes a lot of sense.

I'm all for it!

[mhelmetag]

It would be great to make sure all the numeric typing literals (e.g. the _i64 in 1_i64) are removed. Those would probably throw off beginners and just add unnecessary complication.

[mhelmetag]

I believe all generators were updated to use JSON.mapping.