feat(kubernetes-backend): Add WebSocket support to kubernetes-backend proxy.

Signed-off-by: Carlos Esteban Lopez <lcarlosesteb@vmware.com>

.changeset/khaki-rocks-do.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-kubernetes-backend': patch
+---
+
+Add WebSocket support to `kubernetes-backend` proxy.

plugins/kubernetes-backend/src/service/KubernetesProxy.ts

@@ -135,20 +135,26 @@ export class KubernetesProxy {
       const logger = this.logger.child({ cluster: originalCluster.name });
       middleware = createProxyMiddleware({
         logProvider: () => logger,
+        ws: true,
         secure: !originalCluster.skipTLSVerify,
         changeOrigin: true,
+        pathRewrite: { [`^${originalReq.baseUrl}`]: '' },
         router: async req => {
-          // Re-evaluate the cluster on each request, in case it has changed
-          const cluster = await this.getClusterForRequest(req);
+          const isWS = req.headers.upgrade === 'websocket';
+          const cluster = isWS
+            ? originalCluster
+            : await this.getClusterForRequest(req);
           const url = new URL(cluster.url);
+          const ca = bufferFromFileOrString('', cluster.caData)?.toString();
+
+          // Re-evaluate the cluster on each request, in case it has changed
           return {
             protocol: url.protocol,
             host: url.hostname,
             port: url.port,
-            ca: bufferFromFileOrString('', cluster.caData)?.toString(),
+            ca,
           };
         },
-        pathRewrite: { [`^${originalReq.baseUrl}`]: '' },
         onError: (error, req, res) => {
           const wrappedError = new ForwardedError(
             `Cluster '${originalCluster.name}' request error`,