[serverless] encode lambda error.msg and error.type (#6438)

## Summary of changes

Encodes `error.msg` and `error.type` like the previously encoded
`error.stack`.


![image](https://github.com/user-attachments/assets/9bf0becf-7960-4106-9b74-132e99f83755)

Related extension changes:
DataDog/datadog-agent#32231
DataDog/datadog-lambda-extension#500

## Reason for change
Prevents the tracer from throwing an exception due to non-ASCII
characters in these header values.

[[SLES-2001] .NET Datadog Tracer throws exception from AWS Lambda
Function](https://datadoghq.atlassian.net/browse/SLES-2001)
[[SVLS-6041] Having non-ascii characters in a stack trace causes an
exception within the
tracer.](https://datadoghq.atlassian.net/browse/SVLS-6041)

## Implementation details
Encodes the string values to UTF-8 bytes and then to a Base64 string.

## Test coverage
Updated tests to check for encoded values.

## Other details
<!-- Fixes #{issue} -->


<!-- ⚠️ Note: where possible, please obtain 2 approvals prior to
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[SLES-2001]:
https://datadoghq.atlassian.net/browse/SLES-2001?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ
[SVLS-6041]:
https://datadoghq.atlassian.net/browse/SVLS-6041?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

Author: shreyamalpani

tracer/src/Datadog.Trace/ClrProfiler/AutoInstrumentation/AWS/Lambda/LambdaRequestBuilder.cs

@@ -53,13 +53,15 @@ WebRequest ILambdaExtensionRequest.GetEndInvocationRequest(Scope scope, bool isE
             var errorMessage = span.GetTag("error.msg");
             if (errorMessage != null)
             {
-                request.Headers.Set(HttpHeaderNames.InvocationErrorMsg, errorMessage);
+                var encodedErrMessage = System.Text.Encoding.UTF8.GetBytes(errorMessage);
+                request.Headers.Set(HttpHeaderNames.InvocationErrorMsg, Convert.ToBase64String(encodedErrMessage));
             }
 
             var errorType = span.GetTag("error.type");
             if (errorType != null)
             {
-                request.Headers.Set(HttpHeaderNames.InvocationErrorType, errorType);
+                var encodedErrType = System.Text.Encoding.UTF8.GetBytes(errorType);
+                request.Headers.Set(HttpHeaderNames.InvocationErrorType, Convert.ToBase64String(encodedErrType));
             }
 
             var errorStack = span.GetTag("error.stack");

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

@@ -133,6 +133,11 @@ protected virtual void HandleHttpRequest(HttpListenerContext ctx)
             string? errorMsg = headers.Get("x-datadog-invocation-error-msg") ?? null;
             string? errorType = headers.Get("x-datadog-invocation-error-type") ?? null;
             string? errorStack = headers.Get("x-datadog-invocation-error-stack") ?? null;
+
+            errorMsg = DecodeBase64(errorMsg);
+            errorType = DecodeBase64(errorType);
+            errorStack = DecodeBase64(errorStack);
+
             var invocation = new EndExtensionRequest(headers, body,  traceId, spanId, samplingPriority, isError, errorMsg, errorType, errorStack);
 
             EndInvocations.Push(invocation);
@@ -147,6 +152,26 @@ protected virtual void HandleHttpRequest(HttpListenerContext ctx)
         ctx.Response.Close();
     }
 
+    private static string? DecodeBase64(string? input)
+    {
+        if (input == null)
+        {
+            return input;
+        }
+
+        try
+        {
+            // Try to decode the string as base64
+            byte[] decodedBytes = Convert.FromBase64String(input);
+            return System.Text.Encoding.UTF8.GetString(decodedBytes);
+        }
+        catch (FormatException)
+        {
+            // If it is not a valid base64 string, return original input
+            return input;
+        }
+    }
+
     private void HandleHttpRequests()
     {
         while (_listener.IsListening)

tracer/test/Datadog.Trace.Tests/LambdaRequestBuilderTests.cs

@@ -3,6 +3,7 @@
 // This product includes software developed at Datadog (https://www.datadoghq.com/). Copyright 2017 Datadog, Inc.
 // </copyright>
 #if NET6_0_OR_GREATER
+using System;
 using System.Net;
 using System.Threading.Tasks;
 using Datadog.Trace.ClrProfiler.AutoInstrumentation.AWS.Lambda;
@@ -84,16 +85,24 @@ public async Task TestGetEndInvocationRequestWithErrorTags()
             await using var tracer = TracerHelper.CreateWithFakeAgent();
             var headers = new WebHeaderCollection().Wrap();
             var scope = LambdaCommon.CreatePlaceholderScope(tracer, headers);
-            scope.Span.SetTag("error.msg", "Exception");
-            scope.Span.SetTag("error.type", "Exception");
-            scope.Span.SetTag("error.stack", "everything is " + System.Environment.NewLine + "fine");
+
+            var errorMsg = "Exception";
+            var errorType = "Exception";
+            var errorStack = "everything is " + System.Environment.NewLine + "fine";
+            scope.Span.SetTag("error.msg", errorMsg);
+            scope.Span.SetTag("error.type", errorType);
+            scope.Span.SetTag("error.stack", errorStack);
+
+            var expectedErrorMsg = Convert.ToBase64String(System.Text.Encoding.UTF8.GetBytes(errorMsg));
+            var expectedErrorType = Convert.ToBase64String(System.Text.Encoding.UTF8.GetBytes(errorType));
+            var expectedErrorStack = Convert.ToBase64String(System.Text.Encoding.UTF8.GetBytes(errorStack));
 
             ILambdaExtensionRequest requestBuilder = new LambdaRequestBuilder();
             var request = requestBuilder.GetEndInvocationRequest(scope, true);
             request.Headers.Get("x-datadog-invocation-error").Should().NotBeNull();
-            request.Headers.Get("x-datadog-invocation-error-msg").Should().Be("Exception");
-            request.Headers.Get("x-datadog-invocation-error-type").Should().Be("Exception");
-            request.Headers.Get("x-datadog-invocation-error-stack").Should().NotBeNull();
+            request.Headers.Get("x-datadog-invocation-error-msg").Should().Be(expectedErrorMsg);
+            request.Headers.Get("x-datadog-invocation-error-type").Should().Be(expectedErrorType);
+            request.Headers.Get("x-datadog-invocation-error-stack").Should().Be(expectedErrorStack);
             request.Headers.Get("x-datadog-tracing-enabled").Should().Be("false");
             request.Headers.Get("x-datadog-sampling-priority").Should().Be("1");
             request.Headers.Get("x-datadog-trace-id").Should().NotBeNull();