models.py

from django.db import models
from django.core.validators import MinLengthValidator
from django.contrib.auth.models import User
from django.conf import settings
from taggit.managers import TaggableManager

class Forum(models.Model) :
    title = models.CharField(
            max_length=200,
            validators=[MinLengthValidator(5, "Title must be greater than 5 characters")]
    )
    text = models.TextField()

    # https://django-taggit.readthedocs.io/en/latest/api.html#TaggableManager
    tags = TaggableManager(blank=True)

    owner = models.ForeignKey(settings.AUTH_USER_MODEL, 
        on_delete=models.CASCADE, related_name='tagme_owner')
    comments = models.ManyToManyField(settings.AUTH_USER_MODEL, 
        through='Comment', related_name='tagme_comments')

    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    # Shows up in the admin list
    def __str__(self):
        return self.title

class Comment(models.Model) :
    text = models.TextField(
        validators=[MinLengthValidator(3, "Comment must be greater than 3 characters")]
    )

    forum = models.ForeignKey(Forum, on_delete=models.CASCADE)
    owner = models.ForeignKey(settings.AUTH_USER_MODEL, 
        on_delete=models.CASCADE, related_name='tagme_comment_owner')

    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    # Shows up in the admin list
    def __str__(self):
        if len(self.text) < 15 : return self.text
        return self.text[:11] + ' ...'