Headless CMS

We want to develop a custom headless CMS for use in the JIDOKA website, our internal tools and our blog. A headless CMS is a content management systeem that only has a backend and a backoffice UI, used by content editors, but no graphical user interface for presenting the content to end users.
On the frontend side an application that wants to show data stored in a headless CMS will only be able to use the APIs the CMS offers. This means that the frontends are able to be written in any language that is able to do REST/JS API calls.
The goal of the internship is to develop a headless CMS (e.g.: prismic.io and Contentful) with a lot of attention to user friendliness of the content editor UI and to simple and fast REST/JS APIs for content retrieval.