GetEuGasStorage retrieves EU aggregate natural gas storage fill % from GIE AGSI+.
Successful response
GetEuGasStorageResponse contains the EU aggregate gas storage snapshot.
Current storage fill level as a percentage of working gas volume (0–100).
1-day change in fill percentage (positive = injecting, negative = withdrawing).
Approximate days of consumption remaining at average EU winter drawdown rate.
Current storage trend: "injecting", "withdrawing", or "stable".
UTC ms timestamp when seed data was written.
Calendar date of the most recent data point (YYYY-MM-DD).
True when upstream data is unavailable (fallback result).