Change parser to forward all headers

Previous to this changes, only the relevant headers for the hook were
forwarded. Right now, we are keeping all of them and then we are
checking that, required headers, are present.

This should prevent removing the github signature when the proxy does
not validate the request signature.

Author: gnieto

pkg/parser/parser.go

@@ -14,11 +14,17 @@ func Parse(req *http.Request, provider providers.Provider) (*providers.Hook, err
 	}
 
 	for _, header := range provider.GetHeaderKeys() {
-		if req.Header.Get(header) != "" {
-			hook.Headers[header] = req.Header.Get(header)
-			continue
+		if req.Header.Get(header) == "" {
+			return nil, errors.New("Required header '" + header + "' not found in Request")
 		}
-		return nil, errors.New("Required header '" + header + "' not found in Request")
+
+		// Store required headers in the expected casing
+		hook.Headers[header] = req.Header.Get(header)
+	}
+
+	for header := range req.Header {
+		// Store the rest of the headers in any casing
+		hook.Headers[header] = req.Header.Get(header)
 	}
 
 	if body, err := ioutil.ReadAll(req.Body); err != nil {