improve: add available release series to metadata validation error message

When a provider version doesn't match any release series in the metadata,
the error message now includes the list of available release series.
This helps users understand whether the metadata was properly retrieved
and what versions are actually supported.

This change makes troubleshooting easier, especially in cases where
GOPROXY settings affect metadata retrieval.

Signed-off-by: kahirokunn <[email protected]>

Author: kahirokunn

cmd/clusterctl/client/cluster/installer.go

@@ -18,6 +18,7 @@ package cluster
 
 import (
 	"context"
+	"fmt"
 	"sort"
 	"strings"
 	"time"
@@ -320,7 +321,21 @@ func (i *providerInstaller) getProviderContract(ctx context.Context, providerIns
 
 	releaseSeries := latestMetadata.GetReleaseSeriesForVersion(currentVersion)
 	if releaseSeries == nil {
-		return "", errors.Errorf("invalid provider metadata: version %s for the provider %s does not match any release series", provider.Version, provider.InstanceName())
+		availableSeries := []string{}
+		for _, series := range latestMetadata.ReleaseSeries {
+			availableSeries = append(availableSeries, fmt.Sprintf("%d.%d", series.Major, series.Minor))
+		}
+
+		var errorMsg string
+		if len(availableSeries) > 0 {
+			errorMsg = fmt.Sprintf("invalid provider metadata: version %s for the provider %s does not match any release series. Available series: [%s]",
+				provider.Version, provider.InstanceName(), strings.Join(availableSeries, ", "))
+		} else {
+			errorMsg = fmt.Sprintf("invalid provider metadata: version %s for the provider %s does not match any release series. No release series found in metadata",
+				provider.Version, provider.InstanceName())
+		}
+
+		return "", errors.New(errorMsg)
 	}
 
 	compatibleContracts := i.getCompatibleContractVersions(i.currentContractVersion)