title: Typeorm update record in OneToMany relation
body: <p>I have the following two entities with a OneToMany/ManyToOne relation between them:</p>
  <pre><code>@Entity({ name: 'user' })
  export class User {
    @PrimaryGeneratedColumn('increment')
    id: number;
  
    @Column({ type: 'varchar' })
    firstName: string;
  
    @Column({ type: 'varchar' })
    lastName: string;
  
    @ManyToOne(() =&gt; Group, group =&gt; group.id)
    @JoinColumn({ name: 'groupId' })
    group: Group;
  
    @Column({ type: 'integer' })
    groupId: number;
  }
  </code></pre>
  <pre><code>@Entity({ name: 'group' })
  export class Group {
    @PrimaryGeneratedColumn('increment')
    id: number;
  
    @Column({ type: 'varchar' })
    name: string;
  
    @OneToMany(() =&gt; User, user =&gt; user.group)
    members: User[];
  }
  </code></pre>
  <p>When I create a new group in my Group repository, I can add existing members as follows:</p>
  <pre><code>const group = new Group();
  group.name = 'Test';
  group.members = [{ id: 1 }, { id: 2 }]; // user ids
  this.save(group);
  </code></pre>
  <p>I am wondering if I can update existing members in a similar way. For example if a group with id 1 has two members:</p>
  <pre><code>{ id: 1, firstName: 'Member', lastName: 'One', groupId: 1 }
  { id: 2, firstName: 'Member', lastName: 'Two', groupId: 1 }
  </code></pre>
  <p>Is it possible to update a member through the OneToMany relation in a similar way as I'm adding them ? Something like (making this up):</p>
  <pre><code>const group = await repository.findOne(groupId, { relations: ['members'] });
  group.members = [{ id: 1, firstName: 'Updated' }]; // this would update the firstName of member with id 1 if it exists in the relation
  repository.save(group);
  </code></pre>
  <p>Thanks!</p>