Support for CrossJoin with Subquery in SeaORM

[Ethan1225]

Hello SeaORM team,

I encountered an issue while trying to use CrossJoin with a subquery in SeaORM. My goal was to perform a CROSS JOIN using a subquery, but I ran into some limitations.

Upon checking the implementation, I noticed the following in the TableRefBuilder trait:

pub trait TableRefBuilder: QuotedBuilder {
    /// Translate [`TableRef`] that without values into SQL statement.
    fn prepare_table_ref_iden(&self, table_ref: &TableRef, sql: &mut dyn SqlWriter) {
        match table_ref {
            TableRef::SubQuery(_, _)
            | TableRef::ValuesList(_, _)
            | TableRef::FunctionCall(_, _) => {
                panic!("TableRef with values is not supported")
            }
        }
    }
}

It seems that TableRef::SubQuery (as well as ValuesList and FunctionCall) is not currently supported in SeaORM. Could you please confirm if CROSS JOIN with a subquery is indeed not supported?

If this feature isn't supported yet, are there any plans to add it in the future? Or is there an alternative approach you would recommend for performing a CROSS JOIN with a subquery in SeaORM?

Thank you for your support and for the great work on this library!

Best regards,
Ethan