Write patch extraction metadata directly to STAC API

[VincentVerelst]

• Recommended to add two new environment variables STAC_API_USERNAME and STAC_API_PASSWORD. If these don't exist, authentication will happen via authentication code flow, which will require manual intervention for each batch job, which is not very practical
• Currently URLs point to openeo-dev STAC API, untill we get the correct permissions for POST requests to the prod STAC API (WIP by DevOps)
• Two collections have been created: worldcereal_sentinelx_patch_extractions. We're in talks with the DevOps team to only give PUT, POST and DELETE permissions to the 'wcextractions' account, so that other users cannot accidentally overwrite the STAC metadata. To be seen if this is possible
• One blocking point on the prod STAC API is the non-working /bulk_items/ endpoint. DevOps team is aware.

[VincentVerelst]

@kvantricht , @cbutsko, not ready to be merged until issues above are finished, but the code is ready for review.

[kvantricht]

Looks cool! Not easy for me to understand what happens just from code. Do we need tests for this functionality? Once this thing is kind of operational, we should sit together to have a strategy for ingesting previous extractions as well.

[kvantricht]

Very clean code!! I'll approve and let's see how it goes in practice.