Review IndexFetcher class relevance

[gmaze]

The IndexFetcher is historically the user facade for everything related to Argo index of profiles.

But with the development of the lower level API ArgoIndex, I wonder what's the overall purpose or added value of the IndexFetcher ?

This could even get confusing

We need to review its design against that of ArgoIndex

• Is there any need for a high level index API ?
• Is this somehow contradictory (high-level vs index) ?
• Should we keep the erddap index fetcher ? (so slow !)
• Should manipulation of index be a sub-component of the DataFetcher ?
• In this later scenario, index is supposedly used to explore properties of a selection sampling (how many profiles, which BGC variables available, temporal/seasonal sampling ?, etc ...) before triggering data download.
• [TBC]

[github-actions]

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