Add more datasets to pygeoapi service

[justb4]

There is only one GPKG dataset in the pygeoapi service now. With upcoming demo's e.g. DiS Geo (sept 7, 2021), I propose to add more datasets at least to testbed server, also to demonstrate the variety of input source-files: from CSVs to GPKG and GeoJSON and especially the "proxy" function to unlock existing WFSs and even ESRI Feature Server sources.

For inspiration see some pygeoapi demo services:

• https://demo.pygeoapi.io/covid-19/collections?f=html (uses ESRI FS via OGR Driver for RIVM Covid data!)
• https://demo.pygeoapi.io/stable/collections e.g. https://demo.pygeoapi.io/stable/collections/dutch_windmills (uses RCE WFS v2)

All config and data can be found here: https://github.com/geopython/demo.pygeoapi.io/tree/master/services

[thijsbrentjens]

Good one. Maybe I could do something. Note that @PB-GNM is working on an API for statiscal units, with several collections. That will go to the public demo later, if finished.

But the proxy setup would be nice to have too. Maybe I can do a few things too. But feel free to add it if you feel like it (and it won't cost you much time)

[justb4]

Closing: via #50 have added SU and INSPIRE Addresses datasets.