Add new error handler for catching reportable errors for unary server

[izumin5210]

WHY

I wanna report errors with request contexts...!

WHAT

Add new error handler for catching reportable errors with request parameter and server info.

[codecov-io]

Codecov Report

Merging #12 into master will increase coverage by 4.79%.
The diff coverage is 92.85%.

@@            Coverage Diff             @@
##           master      #12      +/-   ##
==========================================
+ Coverage   57.95%   62.74%   +4.79%     
==========================================
  Files           3        4       +1     
  Lines          88      102      +14     
==========================================
+ Hits           51       64      +13     
- Misses         36       37       +1     
  Partials        1        1

Impacted Files	Coverage Δ
unary_server_error_handlers.go	92.85% <92.85%> (ø)

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