Changed preserveHeaderCase from false to true for request headers.

[Mohammed3194]

I have changed preserveHeaderCase for headers from false to true. The custom headers defined in the back end server were not accepting the case-sensitive header (X-Auth-Signature). The result was that I couldn't make API requests and was getting 401 unauthorized responses all the time.

Once after setting preserveHeaderCase to true API has started working. Consider this change or is that it is possible to change preserveHeaderCase from post/get/put/delete methods, where actual API requests are made.

This is a problem that most others are experiencing as well - #Reference Link

@brianquinlan, @kevmoo, @mit-mit, @natebosch, @devoncarew, @osa1, @Hamaad-Siddiqui, @aam, @guyluz11

Thank You

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[natebosch]

I'm not sure if we need to wait to release this as a major version change with other breaking changes.

https://github.com/dart-lang/http/issues/609

[brianquinlan]

Would this change cause a semantic difference between browser_client and io_client?

[natebosch]

Would this change cause a semantic difference between browser_client and io_client?

I don't think so. I think there is currently a semantic difference and this would remove it. AFAIK the browser does not change the case of headers.

[natebosch]

This change does break some tests, but not many IIRC.