Don't scan outputs which are dust, track dust change as operating costs

Fixes #299.

processor/src/multisigs/mod.rs

@@ -745,9 +745,8 @@ impl<D: Db, N: Network> MultisigManager<D, N> {
           res.push((key, id, tx, eventuality));
         }
 
-        // TODO: If the TX is None, restore its inputs to the scheduler
-        // Otherwise, if the TX had a change output, dropping its inputs would burn funds
-        // Are there exceptional cases upon rotation?
+        // TODO: If the TX is None, restore its inputs to the scheduler for efficiency's sake
+        // If this TODO is removed, also reduce the operating costs
       }
       res
     };

processor/src/multisigs/scanner.rs

@@ -553,7 +553,9 @@ impl<N: Network, D: Db> Scanner<N, D> {
           // TODO: These lines are the ones which will cause a really long-lived lock acquisiton
           for output in network.get_outputs(&block, key).await {
             assert_eq!(output.key(), key);
-            outputs.push(output);
+            if output.amount() >= N::DUST {
+              outputs.push(output);
+            }
           }
 
           for (id, (block_number, tx)) in network

processor/src/multisigs/scheduler.rs

@@ -435,6 +435,7 @@ impl<N: Network> Scheduler<N> {
     let mut remainder = diff - (per_payment * payments_len);
 
     for payment in payments.iter_mut() {
+      // TODO: This usage of saturating_sub is invalid as we *need* to subtract this value
       payment.amount = payment.amount.saturating_sub(per_payment + remainder);
       // Only subtract the remainder once
       remainder = 0;