/transactions/sign doesn't return a signature when sender is missing

[sbrekelmans]

When submitting an unsigned transaction, a "signed" transaction is returned that doesn't contain proofs

After receiving help - it seems I was missing the "sender" address field. The endpoint doesn;t return an error however, it just returns a 200 and a transaction without a proof.

To reproduce, this is the body sent to the endpoint:

{
"type": 4,
"fee": 100000000,
"amount": 1000000000,
"recipient": "",
"senderPublicKey": ""
}

it returns a (200) with a transaction, but missing the "proofs" parameter. I would expect an error.

[sbrekelmans]

Suggestions:

• return a validation error
• add example schema's to the swagger for all POST requests, this would make developing much easier.