K8SPSMDB-1593: Refactor user annotation key generation

pkg/controller/perconaservermongodb/custom_users.go

@@ -105,7 +105,18 @@ func handleUsers(ctx context.Context, cr *api.PerconaServerMongoDB, mongoCli mon
 			continue
 		}
 
-		annotationKey := fmt.Sprintf("percona.com/%s-%s-hash", cr.Name, user.Name)
+		// Kubernetes annotation keys have a limit of 63 characters for the name part
+		// Format: "percona.com/<name>" where it must be less than or equal to 63 characters
+		// We need to keep the "-hash" suffix (5 chars), so we have 58 chars for the prefix
+		annotationKeyBase := fmt.Sprintf("percona.com/%s-%s", cr.Name, user.Name)
+		const hashSuffix = "-hash"
+		const maxAnnotationNameLength = 63
+		const maxPrefixLength = maxAnnotationNameLength - len(hashSuffix)
+
+		if len(annotationKeyBase) > maxPrefixLength {
+			annotationKeyBase = annotationKeyBase[:maxPrefixLength]
+		}
+		annotationKey := fmt.Sprintf("%s%s", annotationKeyBase, hashSuffix)
 
 		if userInfo == nil && !user.IsExternalDB() {
 			err = createUser(ctx, client, mongoCli, &user, sec, annotationKey, userSecretPassKey)