backend: Fix cluster addition

This ensures that:

We only store contexts that actually match the requested cluster name.
We don't return a context key unless we've successfully stored a
context.

Fixes: #2622
Signed-off-by: Kautilya Tripathi <ktripathi@microsoft.com>

Author: Kautilya Tripathi

backend/cmd/stateless.go

@@ -120,7 +120,7 @@ func (c *HeadlampConfig) handleStatelessReq(r *http.Request, kubeConfig string)
 				key = customObj.CustomName + userID
 			}
 		} else if context.Name != clusterName {
-			contextKey = clusterName
+			// Skip contexts that don't match the requested cluster name
 			continue
 		}