Macro impl_join_arg_trait 

macro_rules! impl_join_arg_trait {
    (
        table_trait: $TableTrait:path,
        table_info_trait: $TableInfoTrait:path,
        condition_trait: $ConditionTrait:path,
        value_type: $ValueType:ty $(,)?
    ) => { ... };
}

Macro to generate dialect-specific JoinArg trait and impls.

This consolidates the shared logic for:

• explicit join tuples: (table, condition)
• auto-FK joins for bare tables