Fix an JSON encoding bug for dates.

[jcbriones]

This fixes a date encoding when the Pass or Order model contains a Date.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (b91d21d) to head (669ecde).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main        #6   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            5         5           
  Lines          235       237    +2     
=========================================
+ Hits           235       237    +2     

Files with missing lines	Coverage Δ
Sources/WalletOrders/OrderBuilder.swift	100.00% <100.00%> (ø)
Sources/WalletPasses/PassBuilder.swift	100.00% <100.00%> (ø)

🚀 New features to boost your workflow:

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

[fpseverino]

Thanks!