Final challenge result removal 🎉

[nsmith5]

Summary

• Move uri principal into its own package
• Move username principal into its own package
• Finally remove challenge result code 🎉

[codecov-commenter]

Codecov Report

Merging #626 (1151108) into main (fa41bd9) will increase coverage by 1.04%.
The diff coverage is 93.15%.

@@            Coverage Diff             @@
##             main     #626      +/-   ##
==========================================
+ Coverage   59.86%   60.90%   +1.04%     
==========================================
  Files          26       28       +2     
  Lines        1582     1586       +4     
==========================================
+ Hits          947      966      +19     
+ Misses        558      548      -10     
+ Partials       77       72       -5     

Impacted Files	Coverage Δ
pkg/challenges/challenges.go	40.90% <0.00%> (-19.46%)	⬇️
pkg/identity/uri/principal.go	92.68% <92.68%> (ø)
pkg/identity/username/principal.go	100.00% <100.00%> (ø)

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