Thank you for your contribution and your issue, it's really appreciated. I had a doubt about this point and I wanted to verify about the HTTP headers.

But in the previous version of this RFC7230: https://www.w3.org/Protocols/rfc2616/rfc2616.html

Here is the section 4.2 "Message Headers" of this previous RFC: https://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html#sec4.2
where you have "Field names are case-insensitive".

We can see the RFC2616 was replaced by multiple RFCs (7230-7237) and in the RFC 7230, there is a section 3.2 where there is the description of the header fields.

In the section 3.2 of RFC7230:

3.2. Header Fields
"
Each header field consists of a case-insensitive field name followed
by a colon (":"), optional leading whitespace, the field value, and
optional trailing whitespace.
"

https://tools.ietf.org/html/rfc7230#section-3.2

So in this case, it's case-insensitive.

I think we can close this issue and the associated Pull Request.

Have a nice day and thank you,