Define task schema

[manobi]

enum TaskStatus {
  WAITING
  SCHEDULED
  FAILED
  RUNNING
  DONE
}

type Task {
  id: ID!
  date: DateISOString!
  job: String
  worker: String
  dependencies: [ID]
  status: TaskStatus!
  data: JSONString
  result: JSONString | String
  error: String
  tags: [String]
  duration: Int
  timeout: Int
  retry: Object
  retries: Int
  tags: [String]
  repeat: DateISOInterval
}