Can you add a method to use a JSONObject or JSONArray or JSON String instead of an array of objects?

So basically, instead of using an array of objects for calls, subscriptions and others, we could use either a `JSONObject` or `JSONArray` or JSON text as `String` when calling the `call` or `subscribe` methods, and the `toString()` method of the first 2 things could do what we already have.

Right now, I find it really annoying that I have to create new objects for every type of call I want to do, this would come very very handy and I hope you consider adding it. Thank you.

Start by reading the existing call and subscribe method signatures and how their object-array arguments are converted for DDP messages. Define the supported JSONObject, JSONArray, and String inputs and verify that JSONObject and JSONArray use their toString() output; done means calls and subscriptions accept each form without breaking existing usage.

Written by the indexing model from the issue text.