Fix #36593: use context-path in Grafana redirect

Author: LEDfan

src/main/java/eu/openanalytics/shinyproxy/monitoring/MonitoringController.java

@@ -32,6 +32,7 @@
 import org.springframework.http.HttpStatus;
 import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.servlet.support.ServletUriComponentsBuilder;
 import org.springframework.web.util.UrlPathHelper;
 
 import java.io.IOException;
@@ -61,11 +62,11 @@ public void grafana(HttpServletRequest request, HttpServletResponse response) th
         }
         String uri = urlPathHelper.getPathWithinApplication(request);
         if (uri.equals("/grafana")) {
-            response.sendRedirect("/grafana/");
+            response.sendRedirect(ServletUriComponentsBuilder.fromCurrentContextPath().path("/grafana/").build().toUriString());
             return;
         }
         if (!uri.startsWith("/grafana/")) {
-            throw new IllegalStateException("TODO");
+            throw new IllegalStateException("Invalid Grafana URL");
         }
 
         String target = uri.replace("/grafana/", "/grafana_internal/");