Add documentation on backend selection with load_collection property filtering

[soxofaan]

Covers documentation part of openEOPlatform/architecture-docs#268

[m-mohr]

This looks good, but while reading it my head thinks about whether it is really a good idea to encode this selection into the process graph? It has nothing to do with the actual workflow and as such, may it be better to add this to the "additional" properties for a data processing request (i.e. where VITO also now has the memory options etc.)?

[soxofaan]

whether it is really a good idea to encode this selection into the process graph? It has nothing to do with the actual workflow and as such, may it be better to add this to the "additional" properties for a data processing request (i.e. where VITO also now has the memory options etc.)?

The original idea (bootstrapped at https://github.com/openEOPlatform/architecture-docs/issues/85 ) is to use existing APIs, and making sure it works both for sync and batch jobs.
What you propose requires defining something new (in federation extension), right? And it would not readily be supported in clients I think (at least for sync processing).

[m-mohr]

Yeah, it's more a second thought. It sounds less appealing after a lot of discussions recently about load_collection, filtering and the additional job/sync/service options. Client support is likely limited although allowed by the API (also for synchronous). So it would not be a cheap solution, but is good for a cleaner implementation in the long-run. It's also something that would benefit hugely from Open-EO/openeo-api#471.

Anyway, to not overcomplicate things, let's go for the proposed solution in this PR for now.

[m-mohr]

Looks good, but rendering will likely be broken (see the other comment).

[soxofaan]

done

[m-mohr]

Has been deployed.