models.py :

`class Document(models.Model):
 docfile = models.FileField(upload_to='documents/%Y/%m/%d')
 user = models.ForeignKey(User, null=False, blank= False)`

I have created a model for file upload as shown above. docfile is the field that represents file to be uploaded and user field stores the name of the user that is uploading the file.I want the additional fields so that file uploaded is visible to the ones with whom it has been shared. Tell me the fields for achieving the sharing task.