fix: http header keys are case in-sensitive

[DeepDiver1975]

This is a workaround to get response bodies printed into the log file in case the http response keys are al lower case.

Background: comparing keys case sensitive is wrong as http header keys are case in-sensitive as per definition:

https://www.rfc-editor.org/rfc/rfc7230#section-3.2

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

A true fix requires to work on QNetworkReply::headers(), QHttpHeaders::value() and QHttpHeaders::WellKnownHeader::ContentType .... but this raises the Qt minimum version to 6.8 due to replay->headers()
https://doc.qt.io/qt-6/qnetworkreply.html#headers