[SOLR-8814] Support GeoJSON response format

• Type: New Feature
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 6.1, 7.0
• Component/s: Response Writers
• Assignee: Ryan McKinley
• Reporter: Ryan McKinley
• Created: 09/Mar/16 20:31
• Updated: 17/Jun/16 13:11
• Resolved: 16/Mar/16 19:55

Description

With minor changes, we can modify the existing JSON writer to produce a GeoJSON `FeatureCollection` for ever SolrDocumentList. We can then pick a field to use as the geometry type, and use that for the Feature#geometry

"response":{"type":"FeatureCollection","numFound":1,"start":0,"features":[
      {"type":"Feature",
        "geometry":{"type":"Point","coordinates":[1,2]},
        "properties":{
          ... the normal solr doc fields here ...}}]
  }}

This will allow adding solr results directly to various mapping clients like Leaflet

---

This patch will work with Documents that have a spatial field the either:
1. Extends AbstractSpatialFieldType
2. has a stored value with geojson
2. has a stored value that can be parsed by spatial4j (WKT, etc)

The spatial field is identified with the parameter `geojson.field`