fix: Query parameter serialization

[ahmednfwela]

Description

Fixes #59

Type of Change

• ✨ New feature (non-breaking change which adds functionality)
• 🛠️ Bug fix (non-breaking change which fixes an issue)
• ❌ Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactor
• ✅ Build configuration change
• 📝 Documentation
• 🗑️ Chore

[codecov]

Codecov Report

Attention: Patch coverage is 69.23077% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 32.37%. Comparing base (c907443) to head (583eba2).

Files	Patch %	Lines
packages/oidc_desktop/lib/src/oidc_desktop.dart	0.00%	3 Missing ⚠️
packages/oidc_core/lib/src/utils.dart	87.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #60      +/-   ##
==========================================
+ Coverage   32.00%   32.37%   +0.37%     
==========================================
  Files          44       43       -1     
  Lines        1275     1254      -21     
==========================================
- Hits          408      406       -2     
+ Misses        867      848      -19     

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