Re-add description_hash

Necessary for lnurlpay-enabled wallets

app/services/lndhub.rb

@@ -49,7 +49,8 @@ class Lndhub
   def addinvoice(payload)
     invoice = post "addinvoice", {
       amt: payload[:amount],
-      memo: payload[:memo]
+      memo: payload[:memo],
+      description_hash: payload[:description_hash]
     }
 
     invoice["payment_request"]