🐛 Handle DNS resolution errors in ElastiCache discovery (#6902)

ElastiCache endpoints may not resolve in all regions, causing
discovery to fail with "no such host" errors. Use the existing
IsServiceNotAvailableInRegionError helper to gracefully skip
unavailable regions, matching the pattern used by 12+ other
AWS resources (memorydb, msk, opensearch, etc.).

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: tas50

providers/aws/resources/aws_elasticache.go

@@ -67,6 +67,10 @@ func (a *mqlAwsElasticache) getCacheClusters(conn *connection.AwsConnection) []*
 						log.Warn().Str("region", region).Msg("error accessing region for AWS API")
 						return res, nil
 					}
+					if IsServiceNotAvailableInRegionError(err) {
+						log.Debug().Str("region", region).Msg("elasticache service not available in region")
+						return res, nil
+					}
 					return nil, err
 				}
 				for _, cluster := range clusters.CacheClusters {
@@ -205,6 +209,10 @@ func (a *mqlAwsElasticache) getServerlessCaches(conn *connection.AwsConnection)
 						log.Warn().Str("region", region).Msg("error accessing region for AWS API")
 						return res, nil
 					}
+					if IsServiceNotAvailableInRegionError(err) {
+						log.Debug().Str("region", region).Msg("elasticache service not available in region")
+						return res, nil
+					}
 					return nil, err
 				}
 				for _, cache := range caches.ServerlessCaches {