Support custom graphql scalar types as args

[samueljoli]

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What are you trying to achieve or the steps to reproduce ?

What result did you expect ?

What result did you observe ?

[samueljoli]

const customScalars = require('custom-graphql-scalars');

const Book = Joi.object().keys({
  title: Joi.string()
});

const options = {
  name: 'Book',
  args: {
    id: customScalars.guid()
  }
}