minor: introduced a new endpoint to generate Retrieve Earnings Payment

[saif-software-developer]

A/C:

A new endpoint is created to handle processing the paymentAmount and paymentAddress so that the fee is paid and earnings are distributed

[AndrewWestberg]

I think we should go a different direction with this. We should modify the existing POST v1/earnings/{walletAddress} call to include the wallet utxos (just enough utxos for 3 ada). Then we can also build the transaction in that call and add a cborHex item on the ClaimOrder response. All the information for building the transaction is in that ClaimOrder.

The frontend then needs to just make a single call to the backend to kick off their claiming process.