[Blazor] Form mapping error handling and validation integration for SSR Blazor

[javiercn]

• Implemented error handling and reporting for form data mapping for Minimal APIs and Blazor.

  • Minimal APIs: An exception is throw on the first validation error.
  • Blazor: A callback is provided to capture the errors. Binding continues when no exception
    is thrown from the callback. This enables us to capture as much information as possible in
    the presence of errors.
  • Errors are represented as FormattableString so that the error message can be localized if
    necessary by developers.
  • The error might contain the attempted value to allow redisplaying the correct value on the
    UI.

• Adds support for reporting errors in Blazor. ModelBindingContext captures the errors and the
  attempted values during the binding process and makes them available to the application.

• Updated the FormValueSupplier API to better integrate with model binding.

  • Removed the need for CanConvertSingleValue.
    • We now use the parameter name as part of the path to bind the parameter, for simple and
      complex values.
  • Updated CanBind to enable calling it without a form name when we just want to determine if
    a given type is bindable.
  • Updated the TryBind API to Bind and passed in a context object instead of multiple parameters.

• Integrates with EditForm and EditContext:

  • Updated FieldIdentifier to hold the FieldPath when created from an expression.
  • Added a new ModelBindingValidator to report model binding errors in a form.

[SteveSandersonMS]

Nice one! This looks like a solid implementation and it's great to see the extensive testing. I fully appreciate the design has to cope with multiple different viewpoints on how things work (SSR, interactive, MVC) so good job on balancing all that. Thanks for sorting out theFieldIdentifier-based representation of model errors too.

If we're switching the culture sensitivity by default then it would be ideal to do that in this preview release, but other than that, I'll back out and assume you'll resolve whichever remaining points make sense now and/or file follow-up issues.

[javiercn]

/backport to release/8.0-preview6

[github-actions]

Started backporting to release/8.0-preview6: https://github.com/dotnet/aspnetcore/actions/runs/5379221347