CarterModule cannot be declared as internal #380

Problem
When creating a module using Carter 10.0.0, the class that inherits from ICarterModule must be declared as public.
If I declare it as internal, the Carter framework does not discover or register the module automatically, leading to missing endpoints.

Expected Behavior
ICarterModule should be discoverable even when declared as internal, or the documentation should clearly state that modules must be public.

Actual Behavior

Declaring the module as internal results in no routes being registered.

Changing the module to public fixes the issue.

// This does NOT work — module is not picked up
internal class UserModule : ICarterModule
{
    public void AddRoutes(IEndpointRouteBuilder app) {}
}

// This works
public class UserModule : ICarterModule
{
    public void AddRoutes(IEndpointRouteBuilder app) {}
}