Search vector fields based on `RICH_TEXT` fields were generated using a
treatment on `RICH_TEXT` fields's `body`
column, to only extract and index the core text.
([PR](https://github.com/twentyhq/twenty/pull/7953))
Actually our RICH_TEXT fields are of datatype `text` in our database,
allowing users to insert non-json values, which breaks the search vector
generation (as it expects json values).
Our vision is unclear for now: for instance we may want to turn
RICH_TEXT into a composite field where the plain text would be stored in
a different column.
So for now, we will (1) treat rich_text data as text, and (2) update the
search vector expressions for the existing workspaces.