Better error messages for error on creating app

[treeder]

Doesn't say why:

root@DESKTOP-U7GR405:~# curl -H "Content-Type: application/json" -X POST -d '{
}'>     "app": { "name":"myapp" }
> }' http://localhost:8080/v1/apps
{"error":{"message":"Could not create app"}}

In the logs it's because it already exists