docs: def add_notifications(myclass):
      """
      Decorator which adds fields dynamically to User Notification Settings models.
  
      Each of the keys in the TEXTS dictionary
      are added as a field and DB column.
      """
      for key, value in TEXTS.items():
          # custom notifications cannot be disabled
          if 'custom' in [key, value]:
              continue
  
          field_type = USER_SETTING[key]['type']
  
          if field_type == 'boolean':
              field = models.BooleanField(_(key), default=DEFAULT_BOOLEAN)
          elif field_type == 'distance':
              field = models.IntegerField(
                  _(key),
                  default=DEFAULT_DISTANCE,
                  help_text=_('-1 (less than 0): disabled; 0: enabled for all;\
                              1 (less than 0): enabled for those in the specified distance range (km)')
              )
              field.geo_field = USER_SETTING[key]['geo_field']
  
          field.name = field.column = field.attname = key
          field.user_setting_type = field_type
          setattr(myclass, key, field)
          myclass.add_to_class(key, field)
  
      return myclass