Unable to create polymorphic relationship #298
Description
Support for serializing existing resources with polymorphic relationships was added in #89 but it currently doesn't seem to be possible to create the relationship via JSON API.
The discriminator column does not get set which then results in an error when the new resource is returned and fails to serialize. The discriminator column should be set to the model name which matches the 'type' property of the relationship object in the payload.