Ex2 (integrado): decorator de cache para IWorkshopRepository + TTL por Options

Services/CacheSettings.cs

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+namespace CampusWorkshops.Api.Services;
+
+public sealed class CacheSettings
+{
+    public int DefaultTtlSeconds { get; set; } = 15;
+}

Services/PerRequestClock.cs

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+namespace CampusWorkshops.Api.Services;
+
+public interface IPerRequestClock
+{
+    // Carimbo criado no CONSTRUTOR (não muda depois)
+    DateTimeOffset CreatedAt { get; }
+}
+
+public sealed class PerRequestClock : IPerRequestClock
+{
+    public DateTimeOffset CreatedAt { get; } = DateTimeOffset.UtcNow;
+}

Services/ReportingSingleton.cs

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+using System;
+
+namespace CampusWorkshops.Api.Services;
+
+/// <summary>
+/// Singleton que recebe um Transient (IPerRequestClock).
+/// Na prática, o Transient é resolvido uma única vez, na construção do Singleton,
+/// e "vira" efetivamente singleton dentro dele.
+/// </summary>
+public sealed class ReportingSingleton
+{
+    private readonly IPerRequestClock _clock;
+
+    public ReportingSingleton(IPerRequestClock clock)
+    {
+        _clock = clock;
+    }
+
+    public DateTimeOffset GetClockCreatedAt()
+    {
+        return _clock.CreatedAt;
+    }
+}

Services/RequestId.cs

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+namespace CampusWorkshops.Api.Services;
+
+public interface IRequestIdTransient { Guid Id { get; } }
+public interface IRequestIdScoped    { Guid Id { get; } }
+public interface IRequestIdSingleton { Guid Id { get; } }
+
+internal sealed class RequestIdTransient : IRequestIdTransient { public Guid Id { get; } = Guid.NewGuid(); }
+internal sealed class RequestIdScoped    : IRequestIdScoped    { public Guid Id { get; } = Guid.NewGuid(); }
+internal sealed class RequestIdSingleton : IRequestIdSingleton { public Guid Id { get; } = Guid.NewGuid(); }