`.kraken`: add masked pauses for order req debug

Such that the next time i inevitably must debug the some order-request
error status or precision discrepancy, i have the mkt-symbol branch
ready to go. Also, switch to `'action': 'buy'|'sell' as action,` style
`case` matching instead of the post-`if` predicate style.

piker/brokers/kraken/broker.py

@@ -175,9 +175,8 @@ async def handle_order_requests(
 
             case {
                 'account': 'kraken.spot' as account,
-                'action': action,
-            } if action in {'buy', 'sell'}:
-
+                'action': 'buy'|'sell',
+            }:
                 # validate
                 order = BrokerdOrder(**msg)
 
@@ -262,6 +261,12 @@ async def handle_order_requests(
                 } | extra
 
                 log.info(f'Submitting WS order request:\n{pformat(req)}')
+
+                # NOTE HOWTO, debug order requests
+                #
+                # if 'XRP' in pair:
+                #     await tractor.pause()
+
                 await ws.send_msg(req)
 
                 # placehold for sanity checking in relay loop
@@ -1085,6 +1090,8 @@ async def handle_order_updates(
                         f'Failed to {action} order {reqid}:\n'
                         f'{errmsg}'
                     )
+                    # if tractor._state.debug_mode():
+                    #     await tractor.pause()
 
                     symbol: str = 'N/A'
                     if chain := apiflows.get(reqid):