Content repositories have been around for quite a while. At least Apache Jackrabbit has a RESTful API: https://jackrabbit.apache.org/ https://jackrabbit.apache.

Content repositories have been around for quite a while. At least Apache Jackrabbit has a RESTful API: https://jackrabbit.apache.org/ https://jackrabbit.apache.org/ (for a binding to that API, see for example https://github.com/jackalope/jackalope-jackrabbit https://github.com/jackalope/jackalope-jackrabbit)