This change brings a new SignatureHandler where Presigned.
Requests without Payload are handled very early before even
going through the call.
This change simplifies Donut codebase to not have signature related
logic for all API's.
Simplification is still needed for Payload based signature eg. PUT/POST calls
, which are still part of the donut codebase, which will be done subsequently
after donut re-write.
This convenience was necessary to be used for golang library functions like io.Copy and io.Pipe
where we shouldn't be writing proxies and alternatives returning *probe.Error
This change also brings more changes across code base for clear separation regarding where an error
interface should be passed encapsulating *probe.Error and where it should be used as is.
Harshavardhana