chore(telemetry): track whether tracing was enabled via ssi

Author: mabdinur

tracer/src/Datadog.Trace/Configuration/TracerSettings.cs

@@ -486,6 +486,21 @@ _ when x.ToBoolean() is { } boolean => boolean,
             telemetry.Record(ConfigTelemetryData.SsiInjectionEnabled, value: EnvironmentHelpers.GetEnvironmentVariable("DD_INJECTION_ENABLED"), recordValue: true, ConfigurationOrigins.EnvVars);
             telemetry.Record(ConfigTelemetryData.SsiAllowUnsupportedRuntimesEnabled, value: EnvironmentHelpers.GetEnvironmentVariable("DD_INJECT_FORCE"), recordValue: true, ConfigurationOrigins.EnvVars);
 
+            if (EnvironmentHelpers.GetEnvironmentVariable("DD_INJECTION_ENABLED")?.Contains("tracer") == true)
+            {
+                telemetry.Record(ConfigTelemetryData.InstrumentationSource, "ssi", recordValue: true, ConfigurationOrigins.EnvVars);
+            }
+            else
+            {
+                string? value = EnvironmentHelpers.GetEnvironmentVariable("DD_INSTRUMENTATION_INSTALL_TYPE");
+                if (value != null)
+                {
+                    telemetry.Record(ConfigTelemetryData.InstrumentationSource, value, recordValue: true, ConfigurationOrigins.EnvVars);
+                } else {
+                    telemetry.Record(ConfigTelemetryData.InstrumentationSource, "unknown", recordValue: true, ConfigurationOrigins.EnvVars);
+                }
+            }
+
             if (AzureAppServiceMetadata is not null)
             {
                 telemetry.Record(ConfigTelemetryData.AasConfigurationError, AzureAppServiceMetadata.IsUnsafeToTrace, ConfigurationOrigins.Default);

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

@@ -22,6 +22,7 @@ internal static class ConfigTelemetryData
         public const string CodeHotspotsEnabled = "code_hotspots_enabled";
 
         public const string SsiInjectionEnabled = "ssi_injection_enabled";
+        public const string InstrumentationSource = "instrumentation_source";
         public const string SsiAllowUnsupportedRuntimesEnabled = "ssi_forced_injection_enabled";
 
         // We intentionally are using specific values here, not OR_GREATER_THAN