Entities: Allow References to Table with compound primary keys

[Nobusuma]

Schema example:

interface FinancialAccount : Entity<FinancialAccount> {
    companion object : Entity.Factory<FinancialAccount>()

    val accNumber: Long
    val finInst: FinancialInstitution?
    val finAccType: FinancialAccountType?
}

interface FinancialTransaction : Entity<FinancialTransaction> {
    companion object : Entity.Factory<FinancialTransaction>()

    val transactionId: Long
    val finAcc: FinancialAccount?
    val aliasName: String
}

object FinancialAccounts : Table<FinancialAccount>("financial_account") {
    val accNumber = long("accnumber").primaryKey().bindTo { it.accNumber }
    val finInstCode = varchar("fininstcode").primaryKey().references(FinancialInstitutions) { it.finInst }
    val finAccType = varchar("finacctype").references(FinancialAccountTypes) { it.finAccType }
}

object FinancialTransactions : Table<FinancialTransaction>("Financial_Transaction") {
    val transactionId = long("transactionid").primaryKey().bindTo {it.transactionId}
    val accNumber = long("accnumber").references(FinancialAccounts) {it.finAcc}
    val finInstCode = varchar("fininstcode").references(FinancialAccounts) {it.finAcc}
    val aliasName = varchar("aliasname").bindTo {it.aliasName}
}

When trying to database.financialTransactions.first() I got the following exception

Caused by: java.lang.IllegalStateException: Cannot reference the table 'financial_account' because it has compound primary keys.
	at org.ktorm.schema.BaseTable.checkReferencePrimaryKey(BaseTable.kt:267)
	at org.ktorm.schema.BaseTable.doBindInternal(BaseTable.kt:222)

This happens because the entity FinancialAccount has a two primaries keys (Is a composite key). It would be nice to support this, is a common scenario in a database

[vincentlauvlwj]

Thank you, will consider adding this feature.