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.
HomeboxSearchProvider used to own the RestClient call and item mapping
directly; pulling it into a shared HomeboxItemClient lets the upcoming
sync pipeline page through the same Homebox items without duplicating
the fetch/mapping logic. ConnectionIdentifiable lets both SearchRequest
and SyncRequest be resolved to a connection by the same client.
kasun