Support Map types with itemType about structure

[talyssonoc]

As discusses, we're gonna define the key and item type like this:

{
  permissions: {
    type: Map,
    itemType: { key: String, value: Permission }
  }
}

[LeoGigliotti]

This would be an excellent feature. We are currently working with DynamoDB and we often bump into cases where we want objects with dynamic property naming. This is an excelent use case for saving dictionaries and/or hashtables.

Both JavaScript and DynamoDB supports this use scenario and it would be a great addition to structure.

[loweoj]

Where the value of key is a property on Permission? e.g.

  permissions: {
    type: Map,
    itemType: { key: 'permissionId', value: Permission }
  }

Or does this mean that keys will be coerced to a string?