Implements a REST API that fits into React Admin

For the cloud needs, we want to integrate a new REST API on ARender stack in order to manage OAuth2 client registration.

This REST API should be designed to fit in React Admin in order to use it in the Cloud Dashboard.

This API requires a administrator access and thus configuration on previewer to configure Spring Security.

We need endpoints that:

• save/update/delete an Oauth2 Client
• generate client id and client secret for a new client