fix: add env var to allow sending content for openai python sdk (#8753)

Author: a1exwang

docs/intelligentapps/tracing.md

@@ -378,6 +378,9 @@ from opentelemetry.exporter.otlp.proto.http.trace_exporter import OTLPSpanExport
 from opentelemetry.sdk._events import EventLoggerProvider
 from opentelemetry.exporter.otlp.proto.http._log_exporter import OTLPLogExporter
 from opentelemetry.instrumentation.openai_v2 import OpenAIInstrumentor
+import os
+
+os.environ["OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT"] = "true"
 
 # Set up resource
 resource = Resource(attributes={