HTTP/2 headers should always be lowercase #2
Description
Upon trying to send a request to an HTTP/2 endpoint with custom headers, the request will fail if the headers contain uppercase letters with this error:
PROTOCOL_ERROR(0x1): Protocol error detected: header field names MUST be lowercase
I think we should just always lowercase header names before sending the request, regardless of whether it's HTTP/1.1 or HTTP/2.0. According to RFC2616 and RFC7230, header names are not case sensitive. But... you never know what other implementations will do. So maybe make it a setting. Dunno!