fix(backup): appropriate warning messages for credential data

ref: longhorn/longhorn 7159

Signed-off-by: James Lu <james.lu@suse.com>

datastore/longhorn.go

@@ -313,7 +313,17 @@ func (s *DataStore) ValidateSetting(name, value string) (err error) {
 		for _, checkKey := range checkKeyList {
 			if value, ok := secret.Data[checkKey]; ok {
 				if strings.TrimSpace(string(value)) != string(value) {
-					return fmt.Errorf("there is space or new line in %s", checkKey)
+					switch {
+					case strings.TrimLeft(string(value), " ") != string(value):
+						return fmt.Errorf("invalid leading white space in %s", checkKey)
+					case strings.TrimRight(string(value), " ") != string(value):
+						return fmt.Errorf("invalid trailing white space in %s", checkKey)
+					case strings.TrimLeft(string(value), "\n") != string(value):
+						return fmt.Errorf("invalid leading new line in %s", checkKey)
+					case strings.TrimRight(string(value), "\n") != string(value):
+						return fmt.Errorf("invalid trailing new line in %s", checkKey)
+					}
+					return fmt.Errorf("invalid white space or new line in %s", checkKey)
 				}
 			}
 		}