Feature: Support list type for a field

[chuck-alt-delete]

Is your feature request related to a problem? Please describe.

Datagen doesn’t yet support fields that are lists. I want do to a thing where each order has a list of item ids, then have the item list be the parent field and items.id be the child field.

As a stopgap, I suppose I could make orders an append-only stream with individual item ids instead of a list. I would limit the key space of the order ids to get several items per order. Then I can group by order id and aggregate the item ids into a list

Describe the solution you'd like

I think we would add a case to the record generation function to handle Array type (currently only handles Object and primitive types). There should be one faker method inside the list, and then we generate a random number of elements where the values are generated from the faker method.

For relationships, if the parent field is a list, we would iterate over the list to generate the child records.

[chuck-alt-delete]

As a part of this issue, I would like us to support things like this:

[
    {
        "_meta": {
            "key": "id",
            "topic": "test"
        },
        "id": "datatype.uuid",
        "arr": "helpers.uniqueArray(faker.random.word, 50)"
    }
]

The Faker API has a method called helpers.uniqueArray which can take a function as an input and use that function to generate an array of unique elements. This would be helpful, for example, creating an array of fake product names or ids.