Fix timezone issue in Android Credentials Manager handler

[Widcket]

• All new/changed/fixed functionality is covered by tests (or N/A)
• I have added documentation for all new/changed functionality (or N/A)

📋 Changes

The Android SaveCredentialsRequestHandler receives an expiresAt UTC string date from the Dart layer. This date string should be parsed as UTC, but instead it gets parsed using the default timezone. Thus, the default timezone's offset gets added to the date, resulting in an incorrect Credentials.expiresAt value.

This happens because no timezone was specified for the SimpleDateFormat parser, and as such TimeZone.getDefault() gets used by default.

This PR ensures the SaveCredentialsRequestHandler parses this date as UTC, by setting "UTC" as the parser's timezone.

Before

After

📎 References

Fixes #160

🎯 Testing

Asserts were added to an existing unit test.

[codecov]

Codecov Report

Base: 98.69% // Head: 98.69% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (17a8361) compared to base (e047bca).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #162   +/-   ##
=========================================
  Coverage     98.69%   98.69%           
  Complexity       75       75           
=========================================
  Files            75       75           
  Lines          1377     1378    +1     
  Branches        296      296           
=========================================
+ Hits           1359     1360    +1     
  Misses            6        6           
  Partials         12       12           

Flag	Coverage Δ
auth0_flutter	100.00% <ø> (ø)
auth0_flutter_android	96.53% <100.00%> (+<0.01%)	⬆️
auth0_flutter_ios	100.00% <ø> (ø)
auth0_flutter_platform_interface	99.25% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...edentials_manager/SaveCredentialsRequestHandler.kt	100.00% <100.00%> (ø)

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

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.