sandbox: add support for optional case for new payments

[matm]

Fixes #32

[codecov]

Codecov Report

Merging #33 (fe80704) into main (0f06b79) will not change coverage.
The diff coverage is n/a.

❗ Current head fe80704 differs from pull request most recent head 357d445. Consider uploading reports for the commit 357d445 to get more accurate results

@@           Coverage Diff           @@
##             main      #33   +/-   ##
=======================================
  Coverage   91.02%   91.02%           
=======================================
  Files          12       12           
  Lines         323      323           
=======================================
  Hits          294      294           
  Misses         21       21           
  Partials        8        8           

Impacted Files	Coverage Δ
payments/payment.go	84.21% <ø> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.