[FEATURE REQUEST] GET /projects add Budget Additional services, Billed and Costs

1. We use the function to bill multiple projects via one invoice. But with this we lose the relation of the invoice amounts via get/invoices to the projects. Therefore, currently I cannot determine the billing status of a project via the API data. It would therefore be good to get the current billing status via get/projects.

2. Also, currently the planned budget for additional services marked as "not in budget" cannot be extracted via the API. This should be also possible with get/projects.

3. It would also be nice to get the current costs via get/projects.