Homebox's location fields were flattened into single-purpose keys
(locationName/locationDescription), which gave EmbeddingService no
way to group related fields when rendering vector-store content.
extraData is now Map<String, Map<String, Object>>, letting
HomeboxItemClient express "location" as its own section; buildExtraData
renders each section as a header with indented fields instead of a flat
"Extradata: key: value" line.
kasun