How to pin mat-toolbar and mat-sidenav and only have a scrollbar inside mat-sidenav-content?

See the following StackBlitz for the app in question: https://stackblitz.com/edit/angular-7cazwh?file=src%2Fapp%2Fapp.component.html

<div class="main-div">
  
  <mat-toolbar color="primary" class="app-header">
    <button mat-icon-button (click)="toggleSidenav()">
      <mat-icon>menu</mat-icon>
    </button>
    <span>Config</span>
    <span class="spacer"></span>
    <button mat-icon-button>
      <mat-icon>account_circle</mat-icon>
    </button>
    <span>Admin</span>
  </mat-toolbar>

  <mat-drawer-container class="app-sidenav">
    <mat-drawer #sidenav mode="side" opened="true" class="sidenav" fixedInViewport="false">
      <mat-list>
        <mat-list-item>
          <mat-icon matListIcon>people</mat-icon>Users
        </mat-list-item>
        <mat-list-item>
          <mat-icon matListIcon>devices_other</mat-icon>Devices
        </mat-list-item>
      </mat-list>
    </mat-drawer>
    <mat-drawer-content>
      <p style="margin:20px">TODO: mat-sidenav-content</p>
    </mat-drawer-content>
  </mat-drawer-container>

</div>

.spacer {
  flex: 1 1 auto;
}

.main-div {
  display: grid;
  grid-template-columns: 1fr;
  grid-template-rows: auto 1fr;
  height: 100vh;
}

.app-header {
  grid-column: 1 / 2;
  grid-row: 1 / 2;
}

.app-sidenav {
  grid-column: 1 / 2;
  grid-row: 2 / 3;
}

Currently when the page overflows I end up with the scrollbar on the right side, that spans both the header area (where mat-toolbar is placed) and the content area (where mat-sidenav-content is placed). As shown below:

What I want instead, is the scrollbar to be only shown in the content area as demonstrated below. I want the header and the left side menu to stay pinned (not move while the user is scrolling up and down within the overflowing content):

This scroll is being applied to your body element. You may want to simply reset the margin and padding for the html and body elements:

body, html {
  padding: 0;
  margin: 0;
}

https://stackblitz.com/edit/angular-eddznu?file=src%2Fstyles.css