I am trying to create a Fiori Elements Analytical List Page in VS Code and after selecting my local schema.cds the dropdown for the "Main entity" selection is empty and the following text appears in red: "The OData V4 service you have provided is not suitable for use in an Analytical List Page application. The service must contain aggregate based entity sets for this floorplan."
Where do I find the requirements or examples for making a suitable service with "aggregate based entity sets"?