October 23, 2015
I have investigated how the browser HTTP header can be modified by an browser extension in Chrome. This will be required to let the browser's installed Banking App tell the web-shop that Bitcoin Cheques can be offered. (Or that it can pay by other means.)
The extension allows you to add, modify and remove browser headers.
The result can be watched at this site:
June 1, 2020
I don't think it's possible to do it in the way you are trying to do it.
Indication of the accepted data format is usually done through adding the extension to the resource name. So, if you have resource like
and GET /resources/resource returns its HTML representation, to indicate that you want its XML representation instead, you can use following pattern:
You have to do the accepted content type determination magic on the server side, then.