feat: improve error handling

[abemedia]

• Ignore error's status code if explicitly wrapped with a status code.
• Return 404 on failure to decode path params.
• Text encoder uses TextMarshaler over error
• Remove redundant StatusError code.
• Return correct status code & message for server errors.

[codecov]

Codecov Report

Patch coverage: 69.56% and project coverage change: +1.66 🎉

Comparison is base (5bd82f6) 66.41% compared to head (0c6fee1) 68.07%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #85      +/-   ##
==========================================
+ Coverage   66.41%   68.07%   +1.66%     
==========================================
  Files          23       23              
  Lines         914      899      -15     
==========================================
+ Hits          607      612       +5     
+ Misses        265      244      -21     
- Partials       42       43       +1     

Impacted Files	Coverage Δ
handler.go	80.20% <64.70%> (-1.05%)	⬇️
errors.go	40.00% <75.00%> (+18.46%)	⬆️
encoding/text/encode.go	96.15% <100.00%> (ø)

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