✨ Add verified MVC validation support for OptionalValue<T> with the package OptionalValues.Mvc

[Copilot]

This pull request introduces a new package, OptionalValues.Mvc, which adds ASP.NET Core MVC validation metadata support for the OptionalValue<T> type.

Fixes #31

[desjoerd]

@copilot

This should not be implemented in the main OptionalValues project.

Move the MVC-specific validation behavior into a separate OptionalValues.Mvc package.

Required changes:

• Remove the MVC validation attribute from OptionalValue<T> / SpecifiedValue
• Add a new OptionalValues.Mvc project/package
• Move the MVC-specific tests out of the core test project
• Add MVC-specific tests for this behavior in an OptionalValues.Mvc.Tests project
• Implement this through MVC metadata, not through annotations on the core type

The MVC package should provide an IValidationMetadataProvider / metadata details provider that detects OptionalValue<> and disables child validation for it.

The important behavior is:

context.ValidationMetadata.ValidateChildren = false;

for OptionalValue<>.

This should then be registered through MVC options, for example via an extension method on MvcOptions:

options.ModelMetadataDetailsProviders.Add(
    new OptionalValueValidationMetadataProvider());

or a package-specific helper such as:

options.AddOptionalValuesMvc();

The core OptionalValues package should remain framework-agnostic and should not reference ASP.NET Core MVC abstractions.

[Copilot]

@copilot

This should not be implemented in the main OptionalValues project.
...

Addressed in ec7910d.

The core package no longer contains MVC-specific annotations or references. MVC child-validation suppression now lives in a new OptionalValues.Mvc package via OptionalValueValidationMetadataProvider and MvcOptions.AddOptionalValuesMvc(), with dedicated tests in OptionalValues.Mvc.Tests.

[desjoerd]

@copilot please look at the comments

[desjoerd]

rename to AddOptionalValueSupport to align with the other extension methods.

[Copilot]

@copilot please look at the comments

Addressed in 3431762. The MVC helper is now AddOptionalValueSupport, and OptionalValues.Mvc.Tests now includes controller-integration coverage for both unspecified and specified OptionalValue<T> payloads.

[desjoerd]

@copilot please look at the comments

[Copilot]

@copilot please look at the comments

Addressed in 6ce7ab3.

[Copilot]

@copilot please look at the comments

Addressed in 4804140.