MM-23568: Add rudder to server diagnostics. (#14151)

* MM-23568: Add rudder to server diagnostics.

* Add unit test.

* Go mod tidy.

* CSP Header fix.

* Fix review comments.

* Update web/handlers.go

Co-Authored-By: Jesse Hallam <jesse.hallam@gmail.com>

* Partially address review comments.

* fix tests.

* Finish implementing review suggestions and then fixing tests.

* Fix CSP Header tests.

Co-authored-by: Jesse Hallam <jesse.hallam@gmail.com>

web/handlers.go

@@ -152,7 +152,7 @@ func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("X-Frame-Options", "SAMEORIGIN")
 		// Set content security policy. This is also specified in the root.html of the webapp in a meta tag.
 		w.Header().Set("Content-Security-Policy", fmt.Sprintf(
-			"frame-ancestors 'self'; script-src 'self' cdn.segment.com/analytics.js/%s",
+			"frame-ancestors 'self'; script-src 'self' cdn.rudderlabs.com cdn.segment.com/analytics.js/%s",
 			h.cspShaDirective,
 		))
 	} else {