feat(marshal): allow marshalSaveError function to be specified

The default for this is the same "Temporary logging of sent error"
console.log.  However, this allows the caller to decide to do
something different to save the errors.

packages/marshal/src/marshal.js

@@ -551,7 +551,14 @@ const defaultSlotToValFn = (x, _) => x;
 export function makeMarshal(
   convertValToSlot = defaultValToSlotFn,
   convertSlotToVal = defaultSlotToValFn,
-  { marshalName = 'anon-marshal', errorTagging = 'on' } = {},
+  {
+    marshalName = 'anon-marshal',
+    errorTagging = 'on',
+    // We prefer that the caller instead log to somewhere hidden
+    // to be revealed when correlating with the received error.
+    marshalSaveError = err =>
+      console.log('Temporary logging of sent error', err),
+  } = {},
 ) {
   assert.typeof(marshalName, 'string');
   assert(
@@ -743,12 +750,7 @@ export function makeMarshal(
               if (errorTagging === 'on') {
                 const errorId = nextErrorId();
                 assert.note(val, X`Sent as ${errorId}`);
-                // TODO we need to instead log to somewhere hidden
-                // to be revealed when correlating with the received error.
-                // By sending this to `console.log`, under swingset this is
-                // enabled by `agoric start --reset -v` and not enabled without
-                // the `-v` flag.
-                console.log('Temporary logging of sent error', val);
+                marshalSaveError(val);
                 return harden({
                   [QCLASS]: 'error',
                   errorId,

packages/marshal/src/types.js

@@ -162,7 +162,8 @@
 /**
  * @typedef MakeMarshalOptions
  * @property {string=} marshalName
- * @property {('on'|'off')=} errorTagging
+ * @property {'on'|'off'=} errorTagging
+ * @property {(err: Error) => void=} marshalSaveError
  */
 
 // /////////////////////////////////////////////////////////////////////////////