Added request content logging for Exceptionless.WebApi

[PolitovArtyom]

Adapted solution from Exceptionless.AspNetCore

But really, i don't like it. I think we should add settings for enabling this feature and setting log message max content size. Otherwise, changes may affect users with large requests payload.

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[PolitovArtyom]

I've researched problems with synchronus invocation of 'httpContent.ReadAsFormDataAsync()' and 'HttpContent' flush afrer first read.
And there are no solutions. Logging request body in ASP.NET WebApi is potentioally dangerous for external code. So i'm going to close this merge request.

For my case i've implemented plugin with request body logging. If you think plugn may be included in Exceptionless.WebApi, i can create new merge request.

[niemyjski]

Can you please post your plugin code in this issue so others can copy it. That sounds good to me. I'm also going to work putting this behind a flag in other implementations. In the mean time I'm going to close this until we get this tied down as I think there may be a bug with the asp.net core implementation as well