title: TypeORM, Query entity based on relation property
body: <p>I would like to query an entity based on a related property, for instance:</p>
  
  <pre><code>const x = await repo.findOne({ name: 'foo', parent: { name: 'foo' }});
  </code></pre>
  
  <p>but it aways returns a null when I query by its related <code>parent</code></p>
  
  <p>I alread added  : <code>relations: ['parent']</code>, already set relation as <code>{eager:true}</code></p>
  
  <p>When I Query by <code>parent: {id: X}</code> it works. but I must query by its name.</p>
  
  <p>What should I do to get this query working in TypeORM</p>
  
  <p>It would be similar to:</p>
  
  <p>select * from entity inner join parent ... where entity.name = 'foo' and parent.name = 'foo'</p>