check existing data before downloading new data

[kimlee87]

Since data from ERA5-Land is updated with a specific interval, it makes sense to just download the newly updated data and not re-download the old data.

For example: if users already downloaded data from 2021 to 2023, now they trigger a query to download data from 2021 to 2024, will the package alert user about existing data?

Inital thought:

• check for raw data (i.e. downloaded data) in data lake to find out existing periods
  • This requires consistent naming across files at all time (?)
• check for data stored in database
  • only for monthly data for now