Currently there is no way to specify an SSO user when creating an account via the DeveloperAccount CRD.

This is listed as a known limitation and "unimplemented" 

https://access.redhat.com/documentation/en-us/red_hat_3scale_api_management/2.14/html/operating_red_hat_3scale_api_management/provision-threescale-services-via-operator#limitations-capabilities

https://github.com/3scale/3scale-operator/blob/master/doc/operator-application-capabilities.md#limitations-and-unimplemented-functionalities

This RFE is to implement support for this.