chore(BE): update response code for docs & signin page (#23140)

openmetadata-service/src/main/java/org/openmetadata/service/socket/OpenMetadataAssetServlet.java

@@ -21,15 +21,19 @@ import jakarta.servlet.http.HttpServletRequest;
 import jakarta.servlet.http.HttpServletResponse;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
+import java.util.List;
 import org.jetbrains.annotations.Nullable;
 import org.openmetadata.service.config.OMWebConfiguration;
 import org.openmetadata.service.resources.system.IndexResource;
 
 public class OpenMetadataAssetServlet extends AssetServlet {
   private final OMWebConfiguration webConfiguration;
-
   private final String basePath;
 
+  // List of frontend paths that should be whitelisted and serve the index file
+  private static final List<String> WHITELISTED_PATHS = Arrays.asList("/docs", "/signin");
+
   public OpenMetadataAssetServlet(
       String basePath,
       String resourcePath,
@@ -57,8 +61,31 @@ public class OpenMetadataAssetServlet extends AssetServlet {
     }
 
     super.doGet(req, resp);
+
+    // Check if response is 404 and the path should be whitelisted
     if (!resp.isCommitted() && (resp.getStatus() == 404)) {
+      if (isWhitelistedPath(requestUri)) {
+        // Serve index file for whitelisted paths instead of 404
+        resp.setStatus(200);
+        resp.setContentType("text/html");
+        resp.getWriter().write(IndexResource.getIndexFile(this.basePath));
+      } else {
         resp.sendError(404);
       }
     }
+  }
+
+  /**
+   * Check if the given URI path should be whitelisted
+   * @param requestUri The request URI to check
+   * @return true if the path should be whitelisted, false otherwise
+   */
+  private boolean isWhitelistedPath(String requestUri) {
+    for (String whitelistedPath : WHITELISTED_PATHS) {
+      if (requestUri.startsWith(whitelistedPath)) {
+        return true;
+      }
+    }
+    return false;
+  }
 }