fix(rules): store single-label rules with a comp. format for old vers…

…ions (#1334)

(cherry picked from commit d5044df)

src/rubrix/server/tasks/text_classification/service/service.py

@@ -250,6 +250,7 @@ def add_labeling_rule(
         rule:
             The rule
         """
+        self.__normalized_rule__(rule)
         self.__labeling__.add_rule(dataset, rule)
 
     def update_labeling_rule(
@@ -278,6 +279,8 @@ def update_labeling_rule(
         found_rule.label = labels[0] if len(labels) == 1 else None
         if description is not None:
             found_rule.description = description
+
+        self.__normalized_rule__(found_rule)
         self.__labeling__.replace_rule(dataset, found_rule)
         return found_rule
 
@@ -387,3 +390,12 @@ def compute_overall_rules_metrics(self, dataset: TextClassificationDatasetDB):
             total_records=total,
             annotated_records=annotated,
         )
+
+    @staticmethod
+    def __normalized_rule__(rule: LabelingRule) -> LabelingRule:
+        if rule.labels and len(rule.labels) == 1:
+            rule.label = rule.labels[0]
+        elif rule.label and not rule.labels:
+            rule.labels = [rule.label]
+
+        return rule