Add project files.

MyOffice.Web/Identity/ExternalProviders/ExternalProviderValidatorGoogle.cs

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+namespace MyOffice.Web.Identity.ExternalProviders;
+
+using MyOffice.Core.Identity;
+using Domain;
+using Google.Apis.Auth;
+using Microsoft.Extensions.Options;
+
+public class ExternalProviderValidatorGoogle : IExternalProviderValidator
+{
+	private readonly ExternalProvidersConfig _externalProvidersConfig;
+
+	public ExternalProviderValidatorGoogle(
+		IOptions<ExternalProvidersConfig> externalProvidersConfig
+	)
+	{
+		_externalProvidersConfig = externalProvidersConfig.Value;
+
+		Provider = ExternalProvidersConst.PROVIDER_GOOGLE;
+		IsConfigured = _externalProvidersConfig.IsGoogleConfigured();
+	}
+
+	public string Provider { get; }
+	public bool IsConfigured { get; }
+
+	public async Task<ExternalProviderValidatorResult> ValidateAsync(string token)
+	{
+		var settings = new GoogleJsonWebSignature.ValidationSettings()
+		{
+			Audience = new List<string>() { _externalProvidersConfig.Google!.ClientId! }
+		};
+		var result = await GoogleJsonWebSignature.ValidateAsync(token, settings);
+		if (!result.EmailVerified) return ExternalProviderValidatorResult.Failed();
+
+		return ExternalProviderValidatorResult.Success(result.Email, result.EmailVerified, result.Subject, result.Name);
+	}
+}