Review the onboarding process.

[xbarra]

We should review the onboarding process for all hazards.

Checks we should do:

• The data is available.
• The code still works. (The libraries change and part of the code should be adapted).
• All the zarr files are created, meaning that the content generated is the content currently in the buckets.
• The inventory is generated according to the files that have been prepared.
• The onboarding is documented.

This for instance will require tools for comparing inventory files with the bucket (in both directions).

As part of these, we could harmonize the onboarding process and hence their tests.