workflowticket serializer: use the serializer in the create function

[DonHaul]

• ref: Review the WorkflowTicketViewSet create() to use the serializer cern-sis/issues-inspire#544

[drjova]

@DonHaul could you please update the commit message?

[DonHaul]

@drjova what part of the commit message is wrong?

[drjova]

there is no workflowticket serializer application in the project, since we have two different applications we should use something like:

workflows: add a serializer in the WorkflowTicket create

[DonHaul]

thanks understood.