CONCAT does not work

[tomaskir]

When trying to create a custom column using the concat expression, the query fails with:

:status :failed,
   :class java.sql.SQLException,
   :error
   "Dynamic SQL Error; SQL error code = -804; Function unknown; CONCAT [SQLState:39000, ISC error code:335544586]",

From a quick search, it seems that || is used as the string concatenation operator in Firebird: https://firebirdsql.org/refdocs/langrefupd15-concat.html

Is there any way this can be fixed in the driver? It seems there are already similar fixes in src/metabase/driver/firebird.clj, but I don't know Closure sufficiently to submit a PR with a fix.