Add ValidationsSummaryErrors to DataGrid

[DDDenisSobek]

Is your feature request related to a problem? Please describe.
If exceptions happens at updating, adding or deleting of item, I want to show these for the user and want to cancel updating.

Describe the solution you'd like
I would like, that i can write my error text and state in CancellableRowChange, so that it be shown in pop up window and in form of DataGrid.

<DataGrid ... RowUpdating="@Updating">
...
</DataGrid>
@{
  public void Updating(CancellableRowChange<...> args)
  {
    try
    {
    ...
    }
    catch(Exception ex)
    {
      args.ErrorText = ... ;
      args.Status = ValidationStatus.Error;
      args.Cancel = true;
    }
  }
}

[stsrki]

While I can agree it is a good feature maybe it's better to expand on the existing implementation. For example, we currently have these parameters on DataGrid

/// <summary>
/// If true, shows feedbacks for all validations.
/// </summary>
[Parameter] public bool ShowValidationFeedback { get; set; } = false;

/// <summary>
/// If true, shows summary for all validations.
/// </summary>
[Parameter] public bool ShowValidationsSummary { get; set; } = true;

/// <summary>
/// Label for validaitons summary.
/// </summary>
[Parameter] public string ValidationsSummaryLabel { get; set; }

And I can add additional

[Parameter] public string[] ValidationsSummaryErrors { get; set; }

that could be used like

<DataGrid ... RowUpdating="@Updating" ValidationsSummaryErrors="@errors">
...
</DataGrid>
@{
  string[] errors;

  public void Updating(CancellableRowChange<...> args)
  {
    errors = null;

    try
    {
    ...
    }
    catch(Exception ex)
    {
      errors = new string[]{ something};
      args.Cancel = true;
    }
  }
}

[DDDenisSobek]

Yea, this would be ok for me.