title: angular mat-select set default value in form
body: <p>There is a data model with a nested object :</p>
  
  <pre><code>export interface Model {
    someField1:string;
    someField2:string;
    someObject: Object;
  }
  
  export interface Object {
    someField1: string;
    someField2: string;
    someField3: string;
  }
  </code></pre>
  
  <p>there is a form for this model : </p>
  
  <pre><code>formBuilder.group({
    someField1: null,
    someField2: null,
    someObject: formBuilder.group({
      someField1: null,
      someField2: null,
      someField3: null
  })
  </code></pre>
  
  <p>there is an angular component for this object: </p>
  
  <pre><code>  &lt;mat-form-field&gt;
      &lt;mat-select placeholder="Some Object" formGroupName="someObject"&gt;
        &lt;mat-option *ngFor="let object of someObjectes" [value]="object"&gt;
          {{ object.someField1 }}
        &lt;/mat-option&gt;
      &lt;/mat-select&gt;
    &lt;/mat-form-field&gt;
  </code></pre>
  
  <p>I accept a list of objects from the server and let me select one that the user needs. It is necessary that the choice is tied to the form and if the received model already has data about the object, then they should be displayed as a pre-selected item.</p>