Puts a spatial reference into a serialized format that can be used for item typeKeywords.
Note: discards "latestWkid"
In the past we used
JSON.stringify, but that causes problems because
it can include commas which are interpreted by the portal update item call
as being separate typekeywords. With
JSON.stringify, equality was also
dependent on the order of the properties in the spatial reference.
Check https://developers.arcgis.com/web-map-specification/objects/spatialReference/ for more details on what this object looks like.
Function defined in common/src/downloads/build-existing-exports-portal-query.ts:66