https://atheros.ai/blog/graphql-scalars-and-their-input-and-result-coercion

model_schema.graphql

input CreateTaskInput {
  name: String!
  completed: Boolean = false
  state: TaskStateEnum
  taskPriority: Int = 1
  progress: Float = 0
  dueDate: DateTime
}
"""CreateTaskPayload type definition"""
type CreateTaskPayload {
  task: Task!
}
"""An ISO-8601 encoded UTC date string."""
scalar DateTime
type Mutation {
  createTask(input: CreateTaskInput!): CreateTaskPayload
}
type Query {
  tasks: [Task]!
}
type Task {
  id: ID!
  name: String!
  completed: Boolean!
  state: TaskStateEnum!
  progress: Float!
  taskPriority: Int!
  dueDate: DateTime
  createdAt: DateTime!
  updatedAt: DateTime
}
enum TaskStateEnum {
  ASSIGNED
  UNASSIGNED
  IN_PROGRESS
}