Add support for deserializing sketches

Serializing or sending sketches is not supported yet, but as the data pipeline sends these, we want to not fail

Author: andrewlock

tracer/src/Datadog.Trace/Telemetry/DTOs/SketchSeriesData.cs

@@ -0,0 +1,58 @@
+// <copyright file="SketchSeriesData.cs" company="Datadog">
+// Unless explicitly stated otherwise all files in this repository are licensed under the Apache 2 License.
+// This product includes software developed at Datadog (https://www.datadoghq.com/). Copyright 2017 Datadog, Inc.
+// </copyright>
+
+#nullable enable
+
+namespace Datadog.Trace.Telemetry;
+
+internal class SketchSeriesData
+{
+    public SketchSeriesData(string metric, string sketchBase64, bool common)
+    {
+        Metric = metric;
+        SketchBase64 = sketchBase64;
+        Common = common;
+    }
+
+    public SketchSeriesData(string metric, byte[] sketch, bool common)
+    {
+        Metric = metric;
+        Sketch = sketch;
+        Common = common;
+    }
+
+    /// <summary>
+    /// Gets or sets the Metric name. This value will be prefixed with dd.app_telemetry.{namespace}.*
+    /// or dd.instrumentation_telemetry_data.{namespace}.{language}.*
+    /// </summary>
+    public string Metric { get; set; }
+
+    /// <summary>
+    /// Gets or sets a Base64 encoded protobuf representation of a DDSketch. Ignored if <see cref="Sketch"/> is non-empty.
+    /// </summary>
+    public string? SketchBase64 { get; set; }
+
+    /// <summary>
+    /// Gets or sets a binary protobuf representation of a DDSketch. If empty, <see cref="SketchBase64"/> must be non-empty
+    /// </summary>
+    public byte[]? Sketch { get; set; }
+
+    /// <summary>
+    /// Gets or sets a list of tags that will be associated with the points
+    /// </summary>
+    public string[]? Tags { get; set; }
+
+    /// <summary>
+    /// Gets or sets a value indicating whether indicates whether the metric is common or language specific
+    /// This will affect the tags and prefix of the metric, as explained above.
+    /// If this field is missing it defaults to true.
+    /// </summary>
+    public bool Common { get; set; }
+
+    /// <summary>
+    /// Gets or sets one of the following values: “tracers”, “profilers”, “rum”, “appsec”. Per series override for the namespace field on the payload object
+    /// </summary>
+    public string? Namespace { get; set; }
+}

tracer/src/Datadog.Trace/Telemetry/DTOs/SketchesPayload.cs

@@ -0,0 +1,26 @@
+// <copyright file="SketchesPayload.cs" company="Datadog">
+// Unless explicitly stated otherwise all files in this repository are licensed under the Apache 2 License.
+// This product includes software developed at Datadog (https://www.datadoghq.com/). Copyright 2017 Datadog, Inc.
+// </copyright>
+
+#nullable enable
+using System.Collections.Generic;
+
+namespace Datadog.Trace.Telemetry;
+
+internal class SketchesPayload : IPayload
+{
+    public SketchesPayload(ICollection<DistributionMetricData> series)
+    {
+        Series = series;
+    }
+
+    /// <summary>
+    /// Gets or sets the default namespace for the metrics.
+    /// Default to assuming that all metrics are for the tracer.
+    /// Can be overwritten on a per-metric basis
+    /// </summary>
+    public string Namespace { get; set; } = MetricNamespaceConstants.Tracer;
+
+    public ICollection<DistributionMetricData> Series { get; set; }
+}

tracer/src/Datadog.Trace/Telemetry/TelemetryRequestTypes.cs

@@ -20,6 +20,7 @@ internal static class TelemetryRequestTypes
 
         public const string GenerateMetrics = "generate-metrics";
         public const string Distributions = "distributions";
+        public const string Sketches = "sketches";
 
         public const string MessageBatch = "message-batch";
 

tracer/test/Datadog.Trace.TestHelpers/MockTelemetryAgent.cs

@@ -233,6 +233,7 @@ static TelemetryConverter()
                     { TelemetryRequestTypes.AppProductChanged, CreateSerializer<AppProductChangePayload>() },
                     { TelemetryRequestTypes.GenerateMetrics, CreateSerializer<GenerateMetricsPayload>() },
                     { TelemetryRequestTypes.Distributions, CreateSerializer<DistributionsPayload>() },
+                    { TelemetryRequestTypes.Sketches, CreateSerializer<SketchesPayload>() },
                     { TelemetryRequestTypes.RedactedErrorLogs, CreateLogsSerializer() },
                     { TelemetryRequestTypes.AppExtendedHeartbeat, CreateSerializer<AppExtendedHeartbeatPayload>() },
                     { TelemetryRequestTypes.AppClosing, CreateNullPayloadSerializer() },