Add server configuration service and repo

RecNet.Application/Services/Configuration/ConfigService.cs

@@ -0,0 +1,33 @@
+using System.Text.Json;
+using RecNet.Domain.Repositories;
+
+namespace RecNet.Application.Services.Configuration;
+
+public class ConfigService(IServerConfigRepository repository) : IConfigService
+{
+    private static readonly JsonSerializerOptions JsonOptions = new(JsonSerializerDefaults.Web);
+    
+    public async Task<T?> GetAsync<T>(
+        string key, 
+        T? defaultValue = default, 
+        CancellationToken ct = default)
+    {
+        var config = await repository.GetAsync(key, ct);
+        if (config == null)
+            return defaultValue;
+        
+        return JsonSerializer.Deserialize<T>(config.Value, JsonOptions);
+    }
+
+    public async Task SetAsync<T>(
+        string key, 
+        T value, 
+        CancellationToken ct = default)
+    {
+        var json = JsonSerializer.Serialize(value, JsonOptions);
+        
+        await repository.SetAsync(key, json, ct);
+        
+        await repository.SaveChangesAsync(ct);
+    }
+}