add STAC API for data download

[tomkralidis]

User story

As a wis2box user, I want to download and visualize data from WIS2 global services so that I can access data from external sources in a user friendly manner.

Acceptance criteria

• [ ] update pywis-pubsub to download to wis2box-download/TBD
• [ ] wis2box-apiL: provide STAC API on top of MinIO bucket of data downloaded from pywis-pubsub
• [ ] wis2box-ui: add a link to pygeoapi/STAC API

Future options

• [ ] full API treatment (via OAMaps)
• [ ] show as external data notifications (saving the WNMs to ES/API)

Definition of done

• [ ] unit/functional tests added/updated
• [ ] documentation updated
• [ ] live demonstration provided

[tomkralidis]

• @maaikelimper to add data download to bucket
• @tomkralidis to implement API / pygeoapi STAC / S3 plugin to browse