How to perform a Join and a Group by without using raw SQL

[rcasula]

Hi All, I have this schema

@Table
struct Currency {
    let code: String
    let name: String
    let symbol: String
}

@Table
struct Expense {
    let id: UUID
    let name: String
    let amount: Decimal
    let currencyCode: Currency.ID
    let date: Date
}


// I want to achieve this end result:

@Selection
struct ExpenseModel {
    let id: UUID
    let name: String
    let amount: Decimal
    let currency: Currency
    let date: Date
}

@Selection
struct GroupedExpenses {
    let date: Date
    
    @Column(as: [ExpenseModel].JSONRepresentation.self)
    let expenses: [ExpenseModel]
}

and this is the query I'm trying to use:

Expense.
    .order { $0.date.desc(nulls: .last) }
    .join(Currency.all) { $0.currencyCode.eq($1.code) }
    .group(by: \.date)
    .select {
         // What to do here? I should have 2 arguments: expense and currency, 
         // but it seems that I have only one.
    }

If I do the same query without the group by clause, in the select I have 2 arguments correctly resolved, and I can create the ExpenseModel.
Do you have any suggestions?

Thanks in advance