add ability to backups be removed after a number of days

lib/charms/data_platform_libs/v0/s3.py

@@ -137,7 +137,7 @@ def _on_credential_gone(self, event: CredentialsGoneEvent):
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
-LIBPATCH = 4
+LIBPATCH = 5
 
 logger = logging.getLogger(__name__)
 
@@ -481,6 +481,18 @@ def set_s3_api_version(self, relation_id: int, s3_api_version: str) -> None:
         """
         self.update_connection_info(relation_id, {"s3-api-version": s3_api_version})
 
+    def set_delete_older_than_days(self, relation_id: int, days: int) -> None:
+        """Sets the retention days for full backups in application databag.
+
+        This function writes in the application data bag, therefore,
+        only the leader unit can call it.
+
+        Args:
+            relation_id: the identifier for a particular relation.
+            days: the value.
+        """
+        self.update_connection_info(relation_id, {"delete-older-than-days": str(days)})
+
     def set_attributes(self, relation_id: int, attributes: List[str]) -> None:
         """Sets the connection attributes in application databag.
 
@@ -580,6 +592,17 @@ def s3_api_version(self) -> Optional[str]:
 
         return self.relation.data[self.relation.app].get("s3-api-version")
 
+    @property
+    def delete_older_than_days(self) -> Optional[int]:
+        """Returns the retention days for full backups."""
+        if (
+            not self.relation.app
+            or self.relation.data[self.relation.app].get("delete-older-than-days") is None
+        ):
+            return None
+
+        return int(self.relation.data[self.relation.app].get("delete-older-than-days"))
+
     @property
     def attributes(self) -> Optional[List[str]]:
         """Returns the attributes."""