title: Custom PK field on User Model not recognized by Djoser
body: <p>I have recently switched to Djoser for my authentication service in my DRF api.</p>
  <p>I have a slightly tweaked User model where the PK has changed from id to user_id.</p>
  <p>When I call /auth/users/me/ I get the following error:</p>
  <pre><code>django.core.exceptions.FieldError: Cannot resolve keyword 'id' into field. Choices are: date_joined, email, first_name, groups, user_id etc..
  </code></pre>
  <p>This is my current Djoser settings:</p>
  <pre><code>DJOSER = {
      'USER_ID_FIELD': 'user_id',
      'LOGIN_FIELD': 'email',
      'USER_CREATE_PASSWORD_RETYPE': True,
      'USERNAME_CHANGED_EMAIL_CONFIRMATION': True,
      'PASSWORD_CHANGED_EMAIL_CONFIRMATION': True,
      'SEND_CONFIRMATION_EMAIL': True,
      'PASSWORD_RESET_CONFIRM_URL': 'password/reset/confirm/{uid}/{token}',
      'USERNAME_RESET_CONFIRM_URL': 'email/reset/confirm/{uid}/{token}',
      'ACTIVATION_URL': 'activate/{uid}/{token}',
      'SEND_ACTIVATION_EMAIL': True,
      'SERIALIZERS': {
          'user_create': 'bb.serializers.RegisterSerializer',
          'user_delete': 'djoser.serializers.UserDeleteSerializer'
      },
  }
  </code></pre>
  <p>What can I do to change the target primary key to point at user_id?</p>
  <p>Ideally I wouldn't have to change the name of the field to id as I am using this field a lot across the project.</p>
  <p>Any help would be greatly appreciated.</p>
  <p><strong>Extended User Model:</strong></p>
  <pre><code>from django.contrib.auth.models import AbstractUser
  
  class User(AbstractUser):
      user_id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
      is_connected = models.BooleanField(
          _('Connected'),
          default=False,
      )
      class Meta:
          db_table = 'bb_user'
  </code></pre>