Add last update times & meta information as API

[patrick-zippenfenig]

Return update times of used datasets for a given coordinate as well as which models are selected for best match with attribution.

Information:

• Model
• Source
• License
• Attribution / URL
• Spatial Resolution
• Temporal Resolution (including step down to 3 or 6 hourly)
• Last update time
• Update frequency
• Optional: List of available weather variables
• Optional: Estimated time of next update / Current progress in downloading and conversion

[roe-dl]

Is there new regarding last update time? I would suggest to use the Last-Modified HTTP header field. This would include the possibility to use the If-Modified-Since HTTP feature to reduce server load.

[patrick-zippenfenig]

#963 now starts to systematically record model update times. It will still take a while before last-update headers can be exposed, but it is making progress

[patrick-zippenfenig]

Model update timings are now available. This forms the foundation for more metadata.