feat: add available providers list

ApiDto/Common/OAuthProvider.cs

@@ -0,0 +1,22 @@
+namespace Mirea.Api.Dto.Common;
+
+/// <summary>
+/// Represents different OAuth providers for authentication.
+/// </summary>
+public enum OAuthProvider
+{
+    /// <summary>
+    /// OAuth provider for Google.
+    /// </summary>
+    Google,
+
+    /// <summary>
+    /// OAuth provider for Yandex.
+    /// </summary>
+    Yandex,
+
+    /// <summary>
+    /// OAuth provider for Mail.ru.
+    /// </summary>
+    MailRu
+}

ApiDto/Responses/AvailableProvidersResponse.cs

@@ -0,0 +1,25 @@
+using Mirea.Api.Dto.Common;
+using System;
+
+namespace Mirea.Api.Dto.Responses;
+
+/// <summary>
+/// Represents the response containing information about available OAuth providers.
+/// </summary>
+public class AvailableProvidersResponse
+{
+    /// <summary>
+    /// Gets or sets the name of the OAuth provider.
+    /// </summary>
+    public required string ProviderName { get; set; }
+
+    /// <summary>
+    /// Gets or sets the enum value representing the OAuth provider.
+    /// </summary>
+    public OAuthProvider Provider { get; set; }
+
+    /// <summary>
+    /// Gets or sets the redirect URI for the OAuth provider.
+    /// </summary>
+    public required Uri Redirect { get; set; }
+}