title: Laravel LightHouse GraphQL DateTime Input in Mutation Is Always Null
body: <p>I am learning Laravel and LightHouse and I am trying to create a mutation that takes a DateTime and puts it into the database. Every time I do the mutation through the DateTime that input does not show up and is just labeled as null firing an error in the databases because the table does not allow the DateTime to be null. All of my other values work perfectly fine so I am very confused. The error GraphQL Playground throws is <code>SQLSTATE[23502]: Not null violation: 7 ERROR:  null value in column \&quot;date_of_birth\&quot; violates not-null constraint\nDETAIL:  Failing row contains (17, Blaze, blaze@test.com, null, ABadPassword, null, 2020-08-26 19:54:38, 2020-08-26 19:54:38, null). (SQL: insert into \&quot;users\&quot; (\&quot;username\&quot;, \&quot;password\&quot;, \&quot;email\&quot;, \&quot;updated_at\&quot;, \&quot;created_at\&quot;) values (Blaze, ABadPassword, blaze@test.com, 2020-08-26 19:54:38, 2020-08-26 19:54:38) returning \&quot;id\&quot;)&quot;</code></p>
  <p>This Mutation that was attempted in GraphQL Playground:</p>
  <pre><code>mutation {
   createUser(
    username: &quot;Blaze&quot;
    email: &quot;blaze@test.com&quot;
    password: &quot;ABadPassword&quot;
    date_of_birth: &quot;1998-01-16 00:00:00&quot;
  ){
    id
   }
  }
  </code></pre>
  <p>Here Is my schema:</p>
  <pre><code>&quot;A date string with format `Y-m-d`, e.g. `2011-05-23`.&quot;
  scalar Date @scalar(class: &quot;Nuwave\\Lighthouse\\Schema\\Types\\Scalars\\Date&quot;)
  
  &quot;A datetime string with format `Y-m-d H:i:s`, e.g. `2018-05-23 13:43:32`.&quot;
  scalar DateTime @scalar(class: &quot;Nuwave\\Lighthouse\\Schema\\Types\\Scalars\\DateTime&quot;)
  
  type Mutation {
  createUser(
      username: String @rules(apply: [&quot;required&quot;, &quot;unique:users,username&quot;]),
      password: String @rules(apply: [&quot;required&quot;]),
      email: String @rules(apply: [&quot;required&quot;, &quot;unique:users,email&quot;]),
      date_of_birth: DateTime @rules(apply: [&quot;required&quot;])
  ): User! @create
  }
  
  type User {
    id: ID!
    username: String!
    email: String!
    email_verified_at: DateTime
    password: String!
    created_at: DateTime!
    updated_at: DateTime!
    date_of_birth: DateTime!
  }
  </code></pre>
  <p>Here is my User from the User.php file in the app:</p>
  <pre><code>&lt;?php
  
  namespace App;
  
  use Illuminate\Contracts\Auth\MustVerifyEmail;
  use Illuminate\Foundation\Auth\User as Authenticatable;
  use Illuminate\Notifications\Notifiable;
  
  class User extends Authenticatable
  {
  use Notifiable;
  
  /**
   * The attributes that are mass assignable.
   *
   * @var array
   */
  protected $fillable = [
      'username', 'email', 'password',
      'date_of_birth' =&gt; 'datetime'
  ];
  
  /**
   * The attributes that should be hidden for arrays.
   *
   * @var array
   */
  protected $hidden = [
      'password', 'remember_token',
  ];
  
  /**
   * The attributes that should be cast to native types.
   *
   * @var array
   */
  protected $casts = [
      'email_verified_at' =&gt; 'datetime',
  ];
  }
  </code></pre>
  <p>And here is my table in the database which was created by a migration:</p>
  <pre><code>DatabaseName=# SELECT * FROM users;
  id | username | email | email_verified_at | password | remember_token | created_at | updated_at| 
  date_of_birth  
  </code></pre>
  <p>Hopefully, this gives enough context for the bug, and thank you for your help in advance.</p>