issues/48: Fix superfluous response.WriteHeader call

[komuw]

• When http.ResponseWriter.WriteHeader() is called more than once, it always produces the error;
  http: superfluous response.WriteHeader call from github.com/komuw/ong/middleware.(*logRW).WriteHeader (log.go:121)
  And the stack trace always points to the ong log middleware. But that does not mean that ong has any issues.
  That error is always produced irrespective of if ong is used. It's how net/http works[2]
• Also note that; if http.ResponseWriter.WriteHeader is not called explicitly, the first call to Write
  will trigger[3] an implicit WriteHeader(http.StatusOK).
• So this PR does not fix the issue(since it is an actual feature of net/http), rather it clarifies that understanding.

1. Fixes: http: superfluous response.WriteHeader call #48
2. http: superfluous response.WriteHeader call #48 (comment)
3. https://github.com/golang/go/blob/go1.20.5/src/net/http/server.go#L141-L159

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.05 🎉

Comparison is base (ff0b7f8) 73.37% compared to head (5aae181) 73.43%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #302      +/-   ##
==========================================
+ Coverage   73.37%   73.43%   +0.05%     
==========================================
  Files          42       42              
  Lines        4782     4792      +10     
==========================================
+ Hits         3509     3519      +10     
  Misses       1021     1021              
  Partials      252      252              

Impacted Files	Coverage Δ
middleware/log.go	68.67% <100.00%> (+4.29%)	⬆️

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