Reference field
Resources can directly link to one another using a Selected resource field. This could be useful for adding a Bio to a team page, creating "featured" content, adding menu items to a category or any other situation where defined links need to be made between content.
Resources that are "referenced" this way will appear in the API response of the referencing resource. For example, the Projects page references 4 individual projects. When viewing this resource, the 4 projects will be included. The data which is included can be set separately using schema modes.
Usage
Add a new resource field by viewing a resource type at Structure > Resource types > {Your resource type} > Manage fields, then clicking "Add field" and choosing Selected resource.
Choose the resource types this field can reference, and set any desired defaults such as a resource that should be referenced by default.
If the referenced resource type has another schema mode besides default, you can ensure it is displayed by visiting Manage schema for the referencing content type and selecting it.
For example, the Overview resource type has a reference to Project resources. First create and configure a new schema mode for Project, then navigate to the schema mode for Overview and ensure that new mode is selected on the project reference field.