fix(secrets): redact provider failure details

src/govoplan_calendar/backend/service.py

@@ -1512,14 +1512,14 @@ def store_caldav_credential(
                     value=secret,
                 )
             ).strip()
-        except Exception as exc:
-            raise CalendarError("Stored sync credential could not be written to its secret provider") from exc
+        except Exception:
+            raise CalendarError("Stored sync credential could not be written to its secret provider") from None
         if not provider_ref:
             raise CalendarError("Secret provider returned an empty credential reference")
         if old_provider_ref and old_provider_ref != provider_ref:
             try:
                 provider.delete_secret(old_provider_ref)
-            except Exception as exc:
+            except Exception:
                 if not _provider_secret_is_absent(provider, old_provider_ref):
                     compensation_failed = False
                     try:
@@ -1534,7 +1534,7 @@ def store_caldav_credential(
                     raise CalendarError(
                         "Previous sync credential could not be deleted from its secret provider; "
                         f"the replacement was not activated{compensation_detail}"
-                    ) from exc
+                    ) from None
         existing.secret_encrypted = None
         existing.metadata_ = {"source_id": source.id, "provider_ref": provider_ref}
     else:
@@ -1619,12 +1619,12 @@ def _delete_calendar_owned_credential(
             )
         try:
             provider.delete_secret(provider_ref)
-        except Exception as exc:
+        except Exception:
             if not _provider_secret_is_absent(provider, provider_ref):
                 raise CalendarError(
                     "Stored sync credential could not be deleted from its secret provider; "
                     "the requested deletion was not completed"
-                ) from exc
+                ) from None
         storage_backend = "external_secret_provider"
     credential.secret_encrypted = None
     credential.metadata_ = {"source_id": source_id} if source_id else {}