Template generation

POST <base_url>/<template_id>

with JSON body of the following format:

    borrower: "<universa_address>",
    // and all non-optional fields and some optional fields as key-value pairs

The anseer in the case of errors:

    status: 'error',
    errors: [
            id: "lender",
            text: "invalid addres",
            details: "entered data is not a valid universa address"
        }, //...

In the case of success:

    status: "OK",
    transactionPack64: "<base64 encoded binary>",
    requiredSignatures: "lender,debtor", // field names from template
    description: "the contract should be signed by both parties and registered with Universa, then debtor will be able to use lent asset"