fix: added swap_to parameter to Invoice class and update tests

[CarlosLugones]

Related to #331. Forgot to include the parameter in the Invoice data class.

Also added it to the tests.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.93%. Comparing base (b4bd1a5) to head (00b77d8).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #332      +/-   ##
==========================================
+ Coverage   87.87%   87.93%   +0.06%     
==========================================
  Files           5        5              
  Lines         198      199       +1     
==========================================
+ Hits          174      175       +1     
  Misses         24       24              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.