Restructure AggregationBinder

[KenitoInc]

The main changes:

• Wrap the required AggregationBinder properties in QueryBinderContext
• Make the AggregationBinder implement IAggregationBinder
• Inject AggregationBinder as an implementation of IAggregationBinder
• Make BindSelect and BindGroupBy methods virtual.
• Remove support for EFClassic

Make AggregationBinder public and extensible

public class AggregationBinder : QueryBinder, IAggregationBinder
{
    public virtual Expression BindSelect(TransformationNode transformationNode, QueryBinderContext context)
    {
    }

    public virtual Expression BindGroupBy(TransformationNode transformationNode, QueryBinderContext context)
    {
    }
}

[gathogojr]

I don't think having an AggregationBinderHelper class that inherits from QueryBinder is good design. You can name this class AggregationBinderExtensions and convert the methods to extension methods. Or move the method to BinderExtensions class

[KenitoInc]

The FlattenReferencedProperties method calls non-static methods in the QueryBinder abstract class (Which is the base class for all query binder classes e.g FilterBinder, SelectExpandBinder).

We use the method inside the ApplyBind(this IAggregationBinder binder, IQueryable source, TransformationNode transformationNode, QueryBinderContext context, out Type resultClrType) extension method which is static.

[gathogojr]

I would probably understand if the class was named AggregationBinderBase but I'd need to be convinced that inheritance is the way to go