[purchasing] add purchase status to json output

dagger/purchasing.nim

@@ -96,3 +96,12 @@ proc wait*(purchase: Purchase) {.async.} =
 
 func id*(purchase: Purchase): array[32, byte] =
   purchase.request.id
+
+func finished*(purchase: Purchase): bool =
+  purchase.future.finished
+
+func error*(purchase: Purchase): ?(ref CatchableError) =
+  if purchase.future.failed:
+    some purchase.future.error
+  else:
+    none (ref CatchableError)

dagger/rest/json.nim

@@ -35,7 +35,9 @@ func `%`*(arr: openArray[byte]): JsonNode =
 
 func `%`*(purchase: Purchase): JsonNode =
   %*{
-    "request": %purchase.request,
-    "offers": %purchase.offers,
-    "selected": %purchase.selected
+    "finished": purchase.finished,
+    "error": purchase.error.?msg,
+    "request": purchase.request,
+    "offers": purchase.offers,
+    "selected": purchase.selected
   }