Adding a New User
mutation {
  createUser(name: "abc", email: "hello@abc.com", username: "abc") {
    user {
      id,
      name,
      email,
      username
    }
    ok
  }
}

Getting All Users List
{
  allUsers {
    edges {
      node {
        name,
        email,
        username
      }
    }
  }
}

Finding a User with Username
{
  findUser(username: "rahulmfg") {
    id,
    name,
    email
  }
}

Updating Username With Email ID
mutation {
  changeUsername(email: "abc@abc.com", username:"newabc") {
    user {
      name,
      email,
      username
    }
  }
}