// Send_Step* functions procedure for integrators:
// 1. call GetUnspentOuts endpoint
// 2. call step1__prepare_params_for_get_decoys to get params for calling RandomOuts; call GetRandomOuts
// 3. call step2__reenterable_… with retVals from Step1 (incl using_outs, RandomOuts)
// 3. call step2__try_… with retVals from Step1 (incl using_outs, RandomOuts)
// 3a. While tx must be reconstructed, re-call step1 passing step2 fee_actually_needed as passedIn_attemptAt_fee, then re-request RandomOuts again, and call step2 again
// 3b. If good tx constructed, proceed to submit/save the tx
// Note: This separation of steps fully encodes SendFunds_ProcessStep