v04 format: idiomatic GeoJSON+STAC message format

[petersilva]

https://github.com/wmo-im/wis2-notification-message

WMO has chosen a format as above. It's still JSON, but everything else is different, and Unknown... subject to experiments and negotiation... v03 is deployed (for HPC mirroring, for example) so cannot really change it. Have to increment the version. This is a first shot at what it looks like:

"id":  value of relPath goes here.
"type": "feature",
"geometry": null, or accept one  from the message.
"properties": {
     old fields go here.
     "baseUrl": "..."
}

* "type": is hard-coded.
* geometry field gets passed on literally.
* "links" gets passed on literally.
* all 'fields' get stored in "properties" instead of at the root.   "BaseURL" is now optional. if present, the retrieval url is built from catenating  baseURL and id.   if missing, then STAC-style "links" should be supplied to provide for retrieval.

"id": value of relPath goes here. "type": "feature", "geometry": null, or accept one from the message. "properties": { old fields go here. "baseUrl": "..." }

• "type": is hard-coded.
• geometry field gets passed on literally.
• "links" gets passed on literally.
• all 'fields' get stored in "properties" instead of at the root. "BaseURL" is now optional. if present, the retrieval url is built from catenating baseURL and id. if missing, then STAC-style "links" should be supplied to provide for retrieval.

[petersilva]

branch v03_issue503 implements this. it works. it looks ugly to me though.

[petersilva]

branch v03_issue503 implements this. it works. it looks ugly to me though, because:

• id with a path in it... it would be a lot more obvious if it was called a path... maybe a relative one. The argument is that people want to use mechanism for api calls, where a path doesn't make sense, except it is part of a hierachy... so... confused.
• why nest things in "properties"... GeoJSON allows for foreign members... it's just bloat.
• the first time someone posts a "FeatureCollection", We drop it as invalid? Since each Feature has an ID... does it then become a collective report? and we download multiple files (1 per feature...?)
• People want "links" which is not JSON but STAC. now have to parse this "links" item, of unclear semantics, how to identify which link to actually download (equivalent to retPath?)

[petersilva]

What happenned since April:

• decided that v03 will stay the internal format.
• v04 is an interchange format, because some clients want that.
• created and encoding class. v04 implemented as an encoding.

[petersilva]

The format is called wis now, and message formats are now encapsulated in the postformat classes. It is implemented... need to follow along, but the work for getting an initial version is done.