Create a new design for a project.

The returned design ID allows you to create a deep link into the Aurora application. That way, you can direct users to a specific design within a specific project. Please note, a design must always belong to a project. Therefore the project_id must always be provided. Optionally you can provide a site_model_design_id in the URI, referencing an existing design to act as a template. The created/returned design will in this case contain a copy of the site model of the provided design. Additionally you can assert the include_design flag to also copy the PV design.