Fix Postgres error when using searchable in tables

[robinvda]

Description

Fixes #18467

Fixes a undefined column error from Postgres when using table search. Also fixes a bug where table search would always force the search term to be lowercase by adding forceSearchCaseInsensitive() to Table (same implementation as in Column).

Visual changes

None

Functional changes

• Code style has been fixed by running the composer cs command.
• Changes have been tested to not break existing functionality.
• Documentation is up-to-date.

[danharrin]

Can you explain more about the case insensitivity fix, I don't really understand it

[robinvda]

Using Postgres, the search term was always forced to lowercase (using Str::lower()). So even if i search for John, it would only find results with john, not John. I'm on holiday for 2 weeks now so if necessary i can further check this when i get back.

[danharrin]

In the query, is lower(column) or just column generated? It should be the first for Postgres