Add AliasVault.SmtpService project, refactor solution structure (#104)

src/AliasVault.Client/Main/Models/FormValidation/StringDateFormatAttribute.cs

@@ -0,0 +1,37 @@
+//-----------------------------------------------------------------------
+// <copyright file="StringDateFormatAttribute.cs" company="lanedirt">
+// Copyright (c) lanedirt. All rights reserved.
+// Licensed under the MIT license. See LICENSE.md file in the project root for full license information.
+// </copyright>
+//-----------------------------------------------------------------------
+
+namespace AliasVault.Client.Models.FormValidation;
+
+using System.ComponentModel.DataAnnotations;
+using System.Globalization;
+
+/// <summary>
+/// Model validation attribute for date strings.
+/// </summary>
+/// <remarks>
+/// Initializes a new instance of the <see cref="StringDateFormatAttribute"/> class.
+/// </remarks>
+/// <param name="format">The date format to validate.</param>
+public class StringDateFormatAttribute(string format) : ValidationAttribute
+{
+    /// <summary>
+    /// Check if the date string is in the correct format.
+    /// </summary>
+    /// <param name="value">The field value.</param>
+    /// <param name="validationContext">ValidationContext.</param>
+    /// <returns>ValidationResult.</returns>
+    protected override ValidationResult IsValid(object? value, ValidationContext validationContext)
+    {
+        if (value is string dateString && DateTime.TryParseExact(dateString, format, CultureInfo.InvariantCulture, DateTimeStyles.None, out _))
+        {
+            return ValidationResult.Success!;
+        }
+
+        return new ValidationResult($"The date must be in the format {format}.", [validationContext.MemberName!]);
+    }
+}