OpenTelemetry trace id for logstash in hex format (#32)

* OpenTelemetry trace id for logstash in hex format

src/etos_lib/logging/filter.py

@@ -25,10 +25,11 @@ def get_current_otel_trace_id() -> str:
     The OpenTelemetry trace id is a big integer by default, which is out of range
     of the type 'long' in Elastic. For this reason the trace id is returned as string.
 
-    If OpenTelemetry is not enabled, this function will return "0".
+    If OpenTelemetry is not enabled, this function will return "00000000000000000000000000000000".
     """
     current_span = trace.get_current_span()
-    return str(current_span.get_span_context().trace_id)
+    trace_id = current_span.get_span_context().trace_id
+    return trace.format_trace_id(trace_id)
 
 
 class EtosFilter(logging.Filter):  # pylint:disable=too-few-public-methods