title: Create object if not exists in Django ImportExportModelAdmin
body: <p>I have these two models:</p>
  <blockquote>
  <p>Profile_model.py</p>
  </blockquote>
  <pre><code>class Profile(models.Model):
      firstname = models.CharField(max_length=200, blank=False)
      lastname = models.CharField(max_length=200, blank=False)
      email = models.CharField(max_length=200, unique=True, blank=False)
      ...
  </code></pre>
  <blockquote>
  <p>Investment_model.py</p>
  </blockquote>
  <pre><code>class Investment(models.Model):
      invested = models.DecimalField(max_digits=9, decimal_places=2, blank=True, null=True)
      profile = models.ForeignKey(Profile, on_delete=models.CASCADE)
      ...
  </code></pre>
  <p>and I have this admin:</p>
  <blockquote>
  <p>Investment_admin.py</p>
  </blockquote>
  <pre><code>class InvestmentResource(resources.ModelResource):
      ...
      firstname = fields.Field(attribute='profile', 
          widget=ForeignKeyWidget(Profile, field='firstname'), 
          column_name='firstname')
      lastname = fields.Field(attribute='profile', 
          widget=ForeignKeyWidget(Profile, field='lastname'), 
          column_name='lastname')
      email = fields.Field(attribute='email', 
          widget=ForeignKeyWidget(Profile, field='email'), 
          column_name='email')
      class Meta:
          model = Investment
          fields = (
              'firstname',
              'lastname',
              'email',
              'invested',)
          
          export_order = fields
  
  
  class InvestmentAdmin(ImportExportModelAdmin, admin.ModelAdmin):
          ...
          resource_class = InvestmentResource
          ...
  </code></pre>
  <p>I am using <code>django</code>'s <code>ImportExportModelAdmin</code> for bulk imports and exports but when I try to import, I get this error:</p>
  <p><a href="https://i.stack.imgur.com/1wkrD.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/1wkrD.png" alt="enter image description here" /></a></p>
  <p>I get that its producing this error because the profile hasn't been created yet. But what do I have to do to implement an <code>update_or_create</code> inside the <code>ImportExportModelAdmin</code>?</p>