Detect HTTP-header cookies via CookieStore change event

Progressive enhancement for Chromium browsers: listen on the
CookieStore change event to catch cookies set by Set-Cookie HTTP
response headers, which the document.cookie setter hook cannot see.
Adds a new "http" cookie source through the full stack.

Signed-off-by: Émile Ré <emile@getprobo.com>

pkg/server/api/cookiebanner/v1/handler.go

@@ -266,6 +266,8 @@ func (h *Handler) handleReportDetectedCookies(w http.ResponseWriter, r *http.Req
 		switch strings.TrimSpace(c.Source) {
 		case "pre-existing":
 			source = coredata.CookieSourcePreExisting
+		case "http":
+			source = coredata.CookieSourceHTTP
 		default:
 			source = coredata.CookieSourceScript
 		}
@@ -358,6 +360,8 @@ func (h *Handler) handleReportDetectedTrackers(w http.ResponseWriter, r *http.Re
 		switch strings.TrimSpace(c.Source) {
 		case "pre-existing":
 			source = coredata.CookieSourcePreExisting
+		case "http":
+			source = coredata.CookieSourceHTTP
 		default:
 			source = coredata.CookieSourceScript
 		}