refactor: linking current user

[cbaker6]

New Pull Request Checklist

• I am not disclosing a vulnerability.
• I am creating this PR in reference to an issue.

Issue Description

• Linking a current user current has duplicate code.
• When a test fails in the CI, it isn't retried to see if it will pass

Related issue: #n/a

Approach

• Refactor linking of current user to reduce duplicate code.
• Run failed tests multiple times to gather more information about reasons for failure

TODOs before merging

• Add tests
• Refactor URL mocker
• Update CI for test failures

[parse-github-assistant]

Thanks for opening this pull request!

• 🎉 We are excited about your hands-on contribution!

[codecov]

Codecov Report

Merging #292 (d1f1010) into main (4734212) will decrease coverage by 0.01%.
The diff coverage is 88.00%.

@@            Coverage Diff             @@
##             main     #292      +/-   ##
==========================================
- Coverage   82.36%   82.34%   -0.02%     
==========================================
  Files         104      104              
  Lines       10659    10664       +5     
==========================================
+ Hits         8779     8781       +2     
- Misses       1880     1883       +3     

Impacted Files	Coverage Δ
Sources/ParseSwift/Objects/ParseUser.swift	79.77% <81.25%> (-0.34%)	⬇️
...Authentication/Protocols/ParseAuthentication.swift	72.16% <100.00%> (+0.88%)	⬆️

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