WebServiceTarget - Enable OptimizeBufferReuse by default & Ability to add HTTP request headers

[snakefoot]

Waiting for NLog ver. 4.5

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This change is 

[codecov-io]

Codecov Report

Merging #1912 into master will increase coverage by <1%.
The diff coverage is 77%.

@@           Coverage Diff           @@
##           master   #1912    +/-   ##
=======================================
+ Coverage      81%     81%   +<1%     
=======================================
  Files         288     288            
  Lines       19840   19881    +41     
  Branches     2339    2345     +6     
=======================================
+ Hits        16135   16185    +50     
- Misses       3109    3113     +4     
+ Partials      596     583    -13

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[snakefoot]

Added support for HttpWebRequest Headers. Not sure if it should be pushed to NLog 5.0, as it is a breaking change.

[304NotModified]

Where is the breaking change?

Is it this one? https://github.com/NLog/NLog/pull/1912/files#diff-d37f2c9ae5632b4d37d050856c577959R220

I think it won't be a breaking change if we restore the body of DoInvoke(object[] parameters, AsyncContinuation continuation) (yes code duplication, but we could add a warning/task)

[snakefoot]

Where is the breaking change? Is it this one?

Yes. This method now throws an exception:

protected override void DoInvoke(object[] parameters, AsyncContinuation continuation)
{
   // method is not used, instead asynchronous overload will be used
   throw new NotImplementedException();
}

As it has been replaced by this override method:

protected override void DoInvoke(object[] parameters, AsyncLogEventInfo logEvent)

[snakefoot]

@304NotModified Now modified the code, so it is no longer a breaking change.

[304NotModified]

\0/ thanks!

[snakefoot]

Updated documentation:

https://github.com/NLog/NLog/wiki/WebService-target