Fix Content model

apps/content/models.py

@@ -2,8 +2,6 @@ from django.db import models
 
 from polymorphic.models import PolymorphicModel
 
-from apps.course.models import Course, Lesson
-
 
 class ImageObject(models.Model):
     image = models.ImageField('Изображение', upload_to='content/imageobject')
@@ -19,13 +17,13 @@ class ImageObject(models.Model):
 
 class Content(PolymorphicModel):
     course = models.ForeignKey(
-        Course, on_delete=models.CASCADE,
+        'course.Course', on_delete=models.CASCADE,
         null=True, blank=True,
         verbose_name='Курс',
         related_name='content',
     )
     lesson = models.ForeignKey(
-        Lesson, on_delete=models.CASCADE,
+        'course.Lesson', on_delete=models.CASCADE,
         null=True, blank=True,
         verbose_name='Урок',
         related_name='content',
@@ -69,11 +67,6 @@ class Video(Content):
 
 
 class Gallery(models.Model):
-    course = models.ForeignKey(
-        Course, on_delete=models.CASCADE,
-        null=True, blank=True,
-        verbose_name='Курс'
-    )
     title = models.CharField('Заголовок', max_length=100, default='')
 
     created_at = models.DateTimeField(auto_now_add=True)