Additional `PayIDClient` Tests

[keefertaylor]

High Level Overview of Change

Add additional tests for PayIDClient

Context of Change

This change brings us to testing parity with the other SDK tests (ex: Xpring-JS tests).

Type of Change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Refactor (non-breaking change that only restructures code)
• [x] Tests (You added tests for code that already exists, or your new feature included in this PR)
• [ ] Documentation Updates
• [ ] Release

Before / After

PayIDClient is now sufficiently tested.

Test Plan

CI

[codecov[bot]]

Codecov Report

Merging #251 into master will increase coverage by 0.42%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #251      +/-   ##
==========================================
+ Coverage   89.26%   89.69%   +0.42%     
==========================================
  Files          42       42              
  Lines         941      941              
==========================================
+ Hits          840      844       +4     
+ Misses        101       97       -4     

Impacted Files	Coverage Δ
XpringKit/PayID/PayIDClient.swift	96.55% <0.00%> (+4.59%)	:arrow_up:

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