Merge commit from fork

* Add safe regex matching with timeouts and validation

* Remove redundant length check

* Remove timeouterror workaround

src/documents/serialisers.py

@@ -71,6 +71,7 @@ from documents.parsers import is_mime_type_supported
 from documents.permissions import get_document_count_filter_for_user
 from documents.permissions import get_groups_with_only_permission
 from documents.permissions import set_permissions_for_object
+from documents.regex import validate_regex_pattern
 from documents.templating.filepath import validate_filepath_template_and_render
 from documents.templating.utils import convert_format_str_to_template_format
 from documents.validators import uri_validator
@@ -141,10 +142,10 @@ class MatchingModelSerializer(serializers.ModelSerializer):
             and self.initial_data["matching_algorithm"] == MatchingModel.MATCH_REGEX
         ):
             try:
-                re.compile(match)
-            except re.error as e:
+                validate_regex_pattern(match)
+            except ValueError as e:
                 raise serializers.ValidationError(
-                    _("Invalid regular expression: %(error)s") % {"error": str(e.msg)},
+                    _("Invalid regular expression: %(error)s") % {"error": str(e)},
                 )
         return match