Allow some means to modify the request message when running on .NET core

[jessegavin]

Describe the feature:

We are using ElasticSearch on AWS. In our situation we need to be able to sign each request to ElasticSearch by adding an Authorization header.

The HttpConnection class provides a protected virtual method named CreateWebRequest. I can extend HttpConnection and override this method to add the Authorization header. This works great. In fact there's a Nuget package which does exactly this. See their AwsHttpConnection implementation.

However, ElasticSearch.Net has a different implementation of HttpConnection for .NET Core which does not provide this same "hook". The CreateHttpRequestMessage method is private static. I can't figure out a way to add the Authorization header required to use NEST to for ES on AWS.

Is this something that could be added?

[gmarz]

I can extend HttpConnection and override this method to add the Authorization header. This works great.

This is also the recommended approach 👍

I don't know why CreateHttpRequestMessage is private static...probably oversight on our part (@Mpdreamz @russcam any ideas?). I think we can and should change it to protected virtual. I also think we can break out the basic auth header section into it's own method so a user doesn't have to re-implement that when overriding.

[russcam]

This looks like an oversight on my part.

++ on making this protected virtual and splitting out the auth header; it would be nice to revisit this further to allow passing own HttpClientHandler implementation to allow customisation of request/response pipeline.