✨ Setup etcd helper and magic onion

DysonNetwork.Shared/Etcd/EtcdService.cs

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+using dotnet_etcd;
+using Etcdserverpb;
+using Grpc.Core;
+
+namespace DysonNetwork.Shared.Etcd;
+
+public class EtcdService(string connectionString) : IEtcdService
+{
+    private readonly EtcdClient _etcdClient = new(connectionString);
+    private long _leaseId;
+    private string? _serviceKey;
+    private readonly CancellationTokenSource _cts = new();
+
+    public async Task RegisterServiceAsync(string serviceName, string serviceAddress, int ttl = 15)
+    {
+        _serviceKey = $"/services/{serviceName}/{Guid.NewGuid()}";
+        var leaseGrantResponse = await _etcdClient.LeaseGrantAsync(new LeaseGrantRequest { TTL = ttl });
+        _leaseId = leaseGrantResponse.ID;
+
+        await _etcdClient.PutAsync(new PutRequest
+        {
+            Key = Google.Protobuf.ByteString.CopyFromUtf8(_serviceKey),
+            Value = Google.Protobuf.ByteString.CopyFromUtf8(serviceAddress),
+            Lease = _leaseId
+        });
+
+        _ = Task.Run(async () =>
+        {
+            while (!_cts.Token.IsCancellationRequested)
+            {
+                try
+                {
+                    await _etcdClient.LeaseKeepAlive(new LeaseKeepAliveRequest { ID = _leaseId },
+                        _ => { }, _cts.Token);
+                    await Task.Delay(TimeSpan.FromSeconds(ttl / 3), _cts.Token);
+                }
+                catch (RpcException)
+                {
+                    // Ignored
+                }
+            }
+        }, _cts.Token);
+    }
+
+    public async Task UnregisterServiceAsync()
+    {
+        if (!string.IsNullOrEmpty(_serviceKey))
+        {
+            await _etcdClient.DeleteRangeAsync(_serviceKey);
+        }
+    }
+
+    public async Task<List<string>> DiscoverServicesAsync(string serviceName)
+    {
+        var prefix = $"/services/{serviceName}/";
+        var rangeResponse = await _etcdClient.GetRangeAsync(prefix);
+        return rangeResponse.Kvs.Select(kv => kv.Value.ToStringUtf8()).ToList();
+    }
+
+    public void Dispose()
+    {
+        _cts.Cancel();
+        if (_leaseId != 0)
+        {
+            _etcdClient.LeaseRevoke(new LeaseRevokeRequest { ID = _leaseId });
+        }
+
+        _etcdClient.Dispose();
+    }
+}

DysonNetwork.Shared/Etcd/EtcdServiceExtensions.cs

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+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Configuration;
+using Grpc.Net.Client;
+using MagicOnion.Client;
+using System;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace DysonNetwork.Shared.Etcd
+{
+    public static class EtcdServiceExtensions
+    {
+        public static IServiceCollection AddEtcdService(this IServiceCollection services, IConfiguration configuration)
+        {
+            var etcdConnectionString = configuration.GetConnectionString("Etcd");
+            services.AddSingleton<IEtcdService>(new EtcdService(etcdConnectionString!));
+            return services;
+        }
+
+        public static IServiceCollection AddMagicOnionService<TService>(this IServiceCollection services)
+            where TService : class, MagicOnion.IService<TService>
+        {
+            services.AddSingleton(serviceProvider =>
+            {
+                var etcdService = serviceProvider.GetRequiredService<IEtcdService>();
+                var serviceName = typeof(TService).Name.TrimStart('I'); // Convention: IMyService -> MyService
+
+                // Synchronously wait for service discovery (or handle asynchronously if preferred)
+                var endpoints = etcdService.DiscoverServicesAsync(serviceName).GetAwaiter().GetResult();
+
+                if (!endpoints.Any())
+                {
+                    throw new InvalidOperationException($"No endpoints found for MagicOnion service: {serviceName}");
+                }
+
+                // For simplicity, use the first discovered endpoint
+                var endpoint = endpoints.First();
+
+                var channel = GrpcChannel.ForAddress(endpoint);
+                return MagicOnionClient.Create<TService>(channel);
+            });
+
+            return services;
+        }
+    }
+}

DysonNetwork.Shared/Etcd/IEtcdService.cs

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+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace DysonNetwork.Shared.Etcd
+{
+    public interface IEtcdService : IDisposable
+    {
+        Task RegisterServiceAsync(string serviceName, string serviceAddress, int ttl = 15);
+        Task UnregisterServiceAsync();
+        Task<List<string>> DiscoverServicesAsync(string serviceName);
+    }
+}