title: `repository.create` strips values of columns that are both arrays and embedded objects
body: <p>Given a simple <code>Foo</code> entity, which in turn contains a collection of <code>Bar</code> objects in mongodb</p>
  
  <p>problem occurs <strong>only if a column is both an array and an embedded object</strong>.</p>
  
  <pre><code>@Entity()
  export class Foo {
    @ObjectIdColumn()
    public id: ObjectID;
  
    @Column()
    public simple: string;
  
    @Column(type =&gt; Bar)
    public collection: Bar[];
  }
  
  export class Bar {
    @Column()
    value: boolean;
  }
  </code></pre>
  
  <p><code>repository.create</code> transforms the raw value</p>
  
  <pre><code>{
    "simple": "string",
    "collection": [
      { "value": true },
      { "value": false }
    ]
  }
  </code></pre>
  
  <p>into simply</p>
  
  <pre><code>{ "simple": "string" }
  </code></pre>
  
  <p>I just took this from <a href="https://github.com/typeorm/typeorm/issues/2342" rel="nofollow noreferrer">https://github.com/typeorm/typeorm/issues/2342</a> but same thing is happening on my end</p>