title: Django ORM join without foreign keys and without raw queries
body: <h1>A</h1>
  
  <pre><code>class AKeywords(models.Model):
      id = models.AutoField(primary_key=True, db_column="kw_id")
      word = models.CharField(max_length=200)
      ...
  
      class Meta:
          managed = False
          db_table = '"A"."Keywords"'
  </code></pre>
  
  <h1>B</h1>
  
  <pre><code>class BKeywords(models.Model):
      id = models.AutoField(primary_key=True, db_column="kw_id")
      word = models.CharField(max_length=200)
      ...
      class Meta:
          managed = False
          db_table = '"B"."Keywords"'
  </code></pre>
  
  <p>I have another model where i would like to perform my join.</p>
  
  <pre><code>class XKeywords(models.Model):
      ...
      k_id = models.IntegerField(blank=True, null=True)
      ...
  
      class Meta:
          managed = False
          db_table = '"public"."XKeywords"'
  </code></pre>
  
  <p>I have two models that are very similar, one comes from a database schema and another from another database schema.
  A third model that will be to join with table A or B has i want.</p>
  
  <p>How can i join model A or B without using foreignkeys and raw queries?</p>