Allow to find types in multiple assemblies

[Dreamescaper]

Created from #28 .

By default, ServiceScan scans types in the assembly, where attributed method is located. It's possible to set assembly to scan explicitly via FromAssemblyOf attribute parameter.
In some cases it might be beneficial to scan not one, but multiple assemblies:

I am implementing module monolith, each module is declared in saperate project and maps its endpoints and adds services with static abstract method.

Currenly it is possible to add multiple assemblies by adding multiple attributes, like:

public static partial class ServiceCollectionExtensions
{
    [GenerateServiceRegistrations(AssignableTo = typeof(IEndpoint), FromAssemblyOf  = typeof(FirstType), CustomHandler = nameof(MapEndpoint))]
    [GenerateServiceRegistrations(AssignableTo = typeof(IEndpoint), FromAssemblyOf  = typeof(SecondType), CustomHandler = nameof(MapEndpoint))]
    public static partial IEndpointRouteBuilder MapEndpoints(this IEndpointRouteBuilder endpoints);

    private static void MapEndpoint<T>(IEndpointRouteBuilder endpoints) where T : IEndpoint
    {
        T.MapEndpoint(endpoints);
    }
}

Does it make sence to allow setting multiple assemblies in the same attribute to make it shorter?
E.g.

public static partial class ServiceCollectionExtensions
{
    [GenerateServiceRegistrations(AssignableTo = typeof(IEndpoint), FromAssemblyOf  = [typeof(FirstType), typeof(SecondType)], CustomHandler = nameof(MapEndpoint))]
    public static partial IEndpointRouteBuilder MapEndpoints(this IEndpointRouteBuilder endpoints);

    private static void MapEndpoint<T>(IEndpointRouteBuilder endpoints) where T : IEndpoint
    {
        T.MapEndpoint(endpoints);
    }
}

While it is a bit shorter, I'm a bit hesitant to add new filter properties, I don't want to end up with tens of properties, which are hard to maintain and are confusing to end users (e.g. does it make sense to add array counterpart for AssignableTo or AttributeFilter properties?).

[rus-art]

I think it would be nice to have opportunity to add assemblies from entire solution, maybe it solves 99% use cases. Or more flexible approach with AssemblyFilter also seems good.
Point is not just in a shorter notation, but also in the maintainability of user code. It is easy to forget to add an attribute or property item during development.

[Dreamescaper]

I assume it makes sense to scan types from all solution projects by default (if FromAssemblyOf is not specified).
I'd like to check how significant is performance impact, but I don't think it will be critical.

[Dreamescaper]

@Thinspeed
Would scanning all references solution project make sense for your use case?

[Thinspeed]

Yes, that is better than my solution

[Dreamescaper]

I have published an updated version, which scans all referenced solution projects by default:
https://www.nuget.org/packages/ServiceScan.SourceGenerator/2.0.2

[rus-art]

It seems that method GetSolutionAssemblies doesn't works properly during entire solution build

        foreach (var reference in compilation.References)
        {
            if (reference is CompilationReference) // <-- here we have only MetadataImageReference
            {
                yield return (IAssemblySymbol)compilation.GetAssemblyOrModuleSymbol(reference);
            }
        }

[Dreamescaper]

I see. That's unfortunate. Apparenty MSBuild does something during the solution build to avoid rebuilding unchanged projects.

I'm inclined to revert this change.
I don't know how to determine if compilation.Reference is from the solution or not relyably.
And I certainly don't want to scan all referenced assemblies from framework and nuget packages, at least by default.

[Dreamescaper]

I have marked version 2.0.2 as deprected, and unlisted from Nuget search.
The default behavior to scan all projects from the current solution is reverted due to being unrelyable.

Instead, I have published updated version 2.1.1, which allows to set AttributeNameFilter to scan multiple assemblies.
I.e. if all your solution project names start with "My.Sln" prefix, you can set it to AttributeNameFilter = "My.Sln.*" to include all projects from the solution.

Thanks for your suggestions, and sorry for the inconvinience.