feat: adding further support for cache control

[andyjmorgan]

This PR aims to add further visibility and control over caching.

• Adding further control over caching of content (5m vs 1h)
• Adding visibility on the cache type created.

Note: using a string with constants as C# doesnt like numbers in enum values and creating a custom converter is probably not something you want.

[Copilot]

Pull Request Overview

This PR enhances cache control functionality by adding support for different Time-To-Live (TTL) durations and providing visibility into cache creation metrics. The changes enable developers to specify cache duration (5 minutes or 1 hour) and receive detailed information about which cache types were created.

• Added TTL property to CacheControl class with predefined duration constants
• Added CacheCreation class to track ephemeral cache token usage by duration
• Updated tests to verify cache creation functionality with different TTL values

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
Anthropic.SDK/Messaging/CacheControl.cs	Added TTL property and duration constants for cache control
Anthropic.SDK/Messaging/MessageResponse.cs	Added CacheCreation class to track cache usage by duration
Anthropic.SDK.Tests/DocumentTests.cs	Updated test to use TTL and verify cache creation metrics
Anthropic.SDK.Tests/CacheControlTests.cs	Enhanced tests with TTL usage and cache creation validation

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[tghamm]

Thanks for the PR! This library actually makes fairly heavy use of converters, would you consider using a converter for this?

Some sample code I gen'd up:

using System;
using System.Text.Json;
using System.Text.Json.Serialization;

public enum CacheDuration
{
    FiveMinutes,
    OneHour
}

public class CacheDurationConverter : JsonConverter<CacheDuration>
{
    public override CacheDuration Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        string? value = reader.GetString();
        return value switch
        {
            "5m" => CacheDuration.FiveMinutes,
            "1h" => CacheDuration.OneHour,
            _ => throw new JsonException($"Invalid cache duration: {value}")
        };
    }

    public override void Write(Utf8JsonWriter writer, CacheDuration value, JsonSerializerOptions options)
    {
        string str = value switch
        {
            CacheDuration.FiveMinutes => "5m",
            CacheDuration.OneHour => "1h",
            _ => throw new JsonException($"Invalid cache duration enum: {value}")
        };
        writer.WriteStringValue(str);
    }
}


using System.Text.Json.Serialization;

public class CacheControl
{
    [JsonPropertyName("type")]
    public CacheControlType Type { get; set; }

    [JsonPropertyName("ttl")]
    [JsonConverter(typeof(CacheDurationConverter))]
    public CacheDuration TTL { get; set; }
}

[andyjmorgan]

added the converter as requested, addressed the copilot concern.

[tghamm]

Awesome, thank you for the contribution, and the quick turn-around on feedback!