opentelemetry-util-http: add http client header attribute env vars

Author: herin049

util/opentelemetry-util-http/src/opentelemetry/util/http/__init__.py

@@ -44,6 +44,12 @@
 OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE = (
     "OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE"
 )
+OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_CLIENT_REQUEST = (
+    "OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_CLIENT_REQUEST"
+)
+OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_CLIENT_RESPONSE = (
+    "OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_CLIENT_RESPONSE"
+)
 
 OTEL_PYTHON_INSTRUMENTATION_HTTP_CAPTURE_ALL_METHODS = (
     "OTEL_PYTHON_INSTRUMENTATION_HTTP_CAPTURE_ALL_METHODS"