v3: Provide IServiceProviderIsService

[dahlbyk]

MEDI v6 adds IServiceProviderIsService, which a handful of our projects have (naively) implemented to satisfy https://www.nuget.org/packages/Microsoft.AspNetCore.Mvc.ApiExplorer. Might as well implement once with passing specs.

[Copilot]

Pull Request Overview

This PR introduces support for the new IServiceProviderIsService interface from MEDI v6, ensuring consumers can query service availability directly.

• Implements StructureMapServiceProviderIsService to conform to IServiceProviderIsService
• Registers the new provider-inquiring service in ContainerExtensions
• Updates tests and package references to target Microsoft.Extensions.DependencyInjection v6

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
test/StructureMap.Microsoft.DependencyInjection.Tests/StructureMapContainerTests.cs	Add assertions for IServiceProviderIsService.IsService
test/StructureMap.Microsoft.DependencyInjection.Tests/StructureMap.Microsoft.DependencyInjection.Tests.csproj	Bump test package references to DI v6
src/StructureMap.Microsoft.DependencyInjection/StructureMapServiceProviderIsService.cs	New implementation of IServiceProviderIsService
src/StructureMap.Microsoft.DependencyInjection/StructureMap.Microsoft.DependencyInjection.csproj	Update DI.Abstractions reference to v6
src/StructureMap.Microsoft.DependencyInjection/ContainerExtensions.cs	Register IServiceProviderIsService in the container profile
src/Directory.Build.props	Bump library version prefix to 3.0.0

Comments suppressed due to low confidence (2)

test/StructureMap.Microsoft.DependencyInjection.Tests/StructureMapContainerTests.cs:63

• [nitpick] The variable name spis is cryptic; consider renaming it to something like isServiceProvider or serviceChecker for clarity.

var spis = container.GetInstance<IServiceProviderIsService>();

src/StructureMap.Microsoft.DependencyInjection/ContainerExtensions.cs:140

• [nitpick] The comment uses the abbreviation MEDI v6, which may not be immediately clear to new readers. Consider expanding it to Microsoft.Extensions.DependencyInjection v6.

// Added in MEDI v6

[dustinsoftware]

I see tests to check that IServiceProviderIsService resolves but not any that verifies the behavior in it. Happy to merge as-is if those aren't trivial to add.