Serialization of CustomFields with the "people" resourceSubtype is impossible

[OliverAbdulrahim]

Issue outlined

Summary
No field in CustomField captures the people_value property given by custom field api endpoints. Example:

Example request

curl -X GET https://app.asana.com/api/1.0/tasks/12345?opt_fields=custom_fields
    ... header stuff ...

Example response

{
  "data": {
    "gid": "12345",
    "custom_fields": [
      {
        "gid": "...",
        "resource_subtype": "people",
        "resource_type": "custom_field",
        "people_value": [
          {
            "gid": "...",
            "resource_type": "user"
          },
          {
            "gid": "...",
            "resource_type": "user"
          }
        ],
        "type": "people"
      }
    ]
  }
}

Relevant part of the response

        "people_value": [
          {
            "gid": "...",
            "resource_type": "user"
          },
          {
            "gid": "...",
            "resource_type": "user"
          }
        ]

• people_value is an array of User resources.

Proposed solution

Changes to CustomField class (Java)
Must implement a field to serialize the people_value object within CustomField.

@SerializedName("people_value")
public Collection<User> peopleValue;