naive: add when %next-batch to rpc-api

pkg/arvo/app/azimuth-rpc.hoon

@@ -143,6 +143,7 @@
     %pending-by-ship       [~ (ship:pending id +.params ship:pending:scry)]
     %pending-by-address    [~ (addr:pending id +.params addr:pending:scry)]
     %status                [~ (status id +.params tx-status:scry)]
+    %next-batch            [~ (next-batch id +.params next-batch:scry)]
     :: %history               [~ (history id +.params all:history:scry)]
   ==
 ::
@@ -222,6 +223,12 @@
         (~(scry agentio bowl) %aggregator /tx/(scot %ux keccak)/status/noun)
     ==
   ::
+  ++  next-batch
+    .^  time
+        %gx
+        (~(scry agentio bowl) %aggregator /next-batch/noun)
+    ==
+  ::
   ++  nonce
     |=  [=ship =address:naive]
     ::  FIXME: use proper type from aggregator/index

pkg/arvo/lib/azimuth-rpc.hoon

@@ -482,6 +482,13 @@
     ~(parse error:json-rpc id)
   [%result id (tx-status:to-json (scry u.keccak))]
 ::
+++  next-batch
+  |=  [id=@t params=(map @t json) when=time]
+  ^-  response:rpc
+  ?.  =((lent ~(tap by params)) 0)
+    ~(params error:json-rpc id)
+  [%result id (time:enjs:format when)]
+::
 :: ++  history
 ::   |=  $:  id=@t
 ::           params=(map @t json)