Add an abstraction for resolving an executable

Product

Hot Chocolate

Is your feature request related to a problem?

An example of the problem can be found in https://github.com/ChilliCream/graphql-platform/pull/6833#issuecomment-2675535475.

The solution you'd like

From Michael, something like:

public interface IExecutableResolver
{
    IExecutable<T> Resolve<T>(object source);
}

Registered in the DI container, this would allow for middleware like the SingleOrDefaultMiddleware to execute SingleOrDefaultAsync on the appropriate IExecutable<T> implementation (f.e. EfQueryableExecutable<T>).

Start by reading the SingleOrDefaultMiddleware context and the existing IExecutable implementations, especially EfQueryableExecutable, then inspect how services are registered in the DI container. Done means introducing a resolver abstraction that selects the appropriate executable implementation for a source and allows SingleOrDefaultAsync to run through it, with tests covering the behavior.