Is your feature request related to a problem? Please describe.
Right now the free-text search implementation includes all of the properties fields.

https://github.com/stac-utils/stac-fastapi-elasticsearch-opensearch/blob/059da7e977368e1d3f6064a3ad00aaacc99470f6/stac_fastapi/elasticsearch/stac_fastapi/elasticsearch/database_logic.py#L586C1-L594C17

Describe the solution you'd like
The spec does not define which fields should be included and which should not, but I think it would be useful to add itemid, itemtitle, collectionid, and collectiontitle in the free-text search fields.