Split backend service templates

[mgerzabek]

After the exceptional theia kick-starter training with Jonas Helming from EclipseSource GmbH I found that it would be good to have an easy starting point for either backend service extensions that calls clients with or without callback.

For that I added two new templates templates/backend-uni which contains the unidirectional backend service sample for clients that call backend services in one direction and templates/backend-bidi which contains the bidirectional backend service sample for clients that call backend services which will also call back to the client.

Thank's for considering…