Endorsement Policies and Submitting Transactions

[mrhamm]

Hi,

I am working on an API implementation (Coinbase Rosetta API) that interfaces our clients with a Fabric network to submit transactions.

Based on the API Specs that we are being asked to follow, the transaction flow for clients needs to happen as follows:
Client requests transaction data from API -> API Returns a formatted, unsigned transaction -> Client signs transaction (offline private key signature) and submits to API -> API Broadcasts the signed transaction to ledger.

However, the Fabric transaction flow requires client signatures at both the endorsing and broadcasting (commit) phase - it isn't exactly clear how to handle this with the above process flow. Is there a way for the client to self-endorse a transaction if clients are allowed as endorsers by the endorsement policy? Alternatively, can Fabric be configured to skip the peer-endorsed proposal response all together, and instead allow the client to directly send a signed commit (without ever getting an endorsement from a peer).

I know this seems contrary to how Fabric works - but in our case it is crucial that the client only signs a transaction payload once as opposed to twice.

Any input or ideas as to how to work around this specification would be appreciated,
Thank you!!