Add Steam auth, platform validators & name gen

RecNet.Infrastructure/Services/Steam/SteamAuthValidator.cs

@@ -0,0 +1,48 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using RecNet.Application.Common.Interfaces;
+using RecNet.Application.Common.PlatformAuth;
+using RecNet.Domain.Common;
+
+namespace RecNet.Infrastructure.Services.Steam;
+
+public class SteamAuthValidator(ISteamAuthService steamAuthService) : IPlatformAuthValidator
+{
+    public PlatformType PlatformType 
+        => PlatformType.Steamworks;
+    
+    public async Task<PlatformAuthResult> ValidateAsync(
+        string platformAuthentication,
+        string platformId,
+        CancellationToken ct = default)
+    {
+        var steamParams = JsonSerializer.Deserialize<SteamPlatformAuth>(platformAuthentication);
+        if (steamParams == null)
+            return PlatformAuthResult.Failure("Invalid authentication");
+        
+        var result = await steamAuthService.AuthorizeAsync(steamParams.Ticket, steamParams.AppId.AppId, ct);
+
+        if (!result.Succeeded || result.SteamId is null)
+            return PlatformAuthResult.Failure("Invalid authentication");
+
+        if (!string.IsNullOrWhiteSpace(platformId) &&
+            platformId != result.SteamId)
+            return PlatformAuthResult.Failure("Nice try");
+
+        return PlatformAuthResult.Success(result.DisplayName);
+    }
+
+    private sealed class SteamPlatformAuth
+    {
+        public required string Ticket { get; set; }
+        
+        public required SteamAppIdAuth AppId { get; set; }
+    }
+    
+    // Splooty, why did you set it up like this ;-;
+    private sealed class SteamAppIdAuth 
+    {
+        [JsonPropertyName("m_AppId")]
+        public required uint AppId { get; set; }
+    }
+}