Comment 2 for bug 1871409

Long discussion on IRC[1]. Bottom line:
* config_drive field in db allows for String(255)
* sean-k-mooney remembers that there is some downstream rackspace dependency that use this to store a uuid of a volume
* the Nova API GET /server/details response defines config_drive as either "True" or "" (empty string) with the meaning of False
* the query filter GET/server/details?config_drive= is rejected today by the schema and directly fixing it would spread the empty string crazyness. Using True and False instead would make a confusion with the GET rsp and might break rackspace
=> API + DB cleanup is needed. Item added to https://etherpad.openstack.org/p/nova-api-cleanup L86

[1] http://eavesdrop.openstack.org/irclogs/%23openstack-nova/%23openstack-nova.2020-04-07.log.html#t2020-04-07T14:37:00