don't strip request body if we don't recognize the request method

[eli-darkly]

This addresses #290 by changing the request-processing behavior from this--

• Is the request method is one of the specific methods that we know can have a body?
• If so, then preserve the request body.
• Otherwise, discard the request body.

--to this:

• Is the request method is one of the specific methods that we know cannot have a body?
• If so, then discard the request body.
• Otherwise, preserve the request body.

For any of the methods that were already listed in BodyParser.cs, this change has no effect: request bodies will still be discarded for GET or DELETE, preserved for POST or PUT, etc. But for methods that were not specifically mentioned there (like REPORT), the request body (if any) will be preserved. I believe this is more in line with the HTTP specification, which only says that a server should discard the body if the method is known not to allow one.

While REPORT was the method I wanted to use in my own code, I didn't bother adding it to this list because it's just one of many rarely-used methods that appear in the HTTP Method Registry.

[codecov]

Codecov Report

Merging #294 into master will increase coverage by 0.03%.
The diff coverage is 89.47%.

@@            Coverage Diff             @@
##           master     #294      +/-   ##
==========================================
+ Coverage   79.72%   79.75%   +0.03%     
==========================================
  Files         108      108              
  Lines        4305     4322      +17     
==========================================
+ Hits         3432     3447      +15     
- Misses        873      875       +2

Impacted Files	Coverage Δ
src/WireMock.Net/Util/BodyParser.cs	90.9% <89.47%> (-0.56%)	⬇️

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[StefH]

Maybe instead of

if (method == null)

Use string.isnullorempty