added image field under assignment

assignments/models.py

 from django.db import models
 
+images_dir = 'assignments/static/assignments/images'
+
 
 class Assignment(models.Model):
     name = models.CharField(max_length=120)
     description = models.TextField(blank=True)
     max_points = models.IntegerField(default=10)
     passing_score = models.IntegerField(default=6)
+    image = models.ImageField(null=True, blank=True, upload_to=images_dir)
 
     def save(self, *args, **kwargs):
         self.passing_score = int(0.6*self.max_points)