Send email on successful bitcoin payin

emails/coinbase_success.spt

@@ -0,0 +1,9 @@
+{{ _("Your Bitcoin payin was successful!") }}
+
+[---] text/html
+{{ _("Your Bitcoin payment for {0} succeeded. Thanks for using Gratipay!",
+     format_currency(amount, 'USD')) }}
+
+[---] text/plain
+{{ _("Your Bitcoin payment for {0} succeeded. Thanks for using Gratipay!",
+     format_currency(amount, 'USD')) }}

www/callbacks/coinbase.spt

@@ -34,13 +34,18 @@ if order:
 
     status = order['status']
 
+    # We're ignoring mispayments/expired orders here.
     if status == 'completed':
         assert order['total_native']['currency_iso'] == 'USD'
         assert order['total_payout']['currency_iso'] == 'USD'
         amount = int(order['total_payout']['cents']) * D('0.01')
         fee = int(order['total_native']['cents']) * D('0.01') - amount
 
         record_exchange(website.db, route, amount, fee, participant, 'succeeded')
-    # TODO - handle mispayments
+        participant.queue_email(
+            'coinbase_success',
+            amount=amount
+        )
+
 
 [---] text/plain