I don't think there's any good reason not to use a TextField there.

dbsettings/models.py

@@ -4,7 +4,7 @@ from django.db import models
 
 class Setting(models.Model):
     key = models.CharField(primary_key=True, max_length=255)
-    value = models.CharField(max_length=255)
+    value = models.TextField()
 
     def __str__(self):
         return self.key