review 2/2: Use generic query to make the code more readable.

Suggested by @cdecker

P.S: Also this include an API refactoring from my previous solution, also this it is suggested by @cdecker.

Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>

Author: vincenzopalazzo

doc/lightning-listsendpays.7

@@ -4,15 +4,15 @@ lightning-listsendpays -- Low-level command for querying sendpay status
 SYNOPSIS
 --------
 
-**listsendpays** \[*bolt11*\] \[*payment\_hash*\] [\*status*\]
+**listsendpays** \[*bolt11*\] \[*payment\_hash*\] \[*status*\]
 
 DESCRIPTION
 -----------
 
 The **listsendpays** RPC command gets the status of all *sendpay*
 commands (which is also used by the *pay* command), or with *bolt11* or
 *payment\_hash* limits results to that specific payment. You cannot
-specify both. It is possible filter the payments also by status.
+specify both. It is possible filter the payments also by *status*.
 
 Note that in future there may be more than one concurrent *sendpay*
 command per *pay*, so this command should be used with caution.