Add the ability to import Other Projects to a project using the REST API
When creating a project using the REST API you should be able to specify linked projects to import. In the UI this is under Files -> Other Projects. There should also be REST API calls to get the list of imported projects, add, remove and update projects.
This would be similar to the API calls for adding Git repositories (see https://dominodatalab.github.io/api-docs/#/reference/projects-v4/connect-git-repositories)