UPDATE DeviceGroup
SET discarded_attrs="null"
WHERE discarded_attrs IS NULL;

ALTER TABLE DeviceGroup
change discarded_attrs discarded_attrs LONGTEXT NOT NULL;
ALTER TABLE DeviceGroup
ALTER discarded_attrs SET DEFAULT "null";
Add valid default value for json column
Add valid default value for json column

 - PRO-1651
 - This commit adds a default, non-null, value for the discarded_attrs
   column in the device registry db. This is to fix 500 errors we got
   due to null values in this column which are unexpected by slick as
   the column does not have an Option type.
