entry: add AdditionalData2

Support metadata as dict property "AdditionalData2".

Tested: Created a new event and ensured property is created.  Reloaded
the daemon with an old event and ensured property exists and is
populated.

```
.AdditionalData2                            property  a{ss}     8 "READING_VALUE" "98.6" "SENSOR_NAME" "Inlet Temperature" "THRESHOLD_VALUE" "40.0" "UNITS" "xyz.openbmc_project.Sensor.Value.Unit.DegreesC" "_CODE_FILE" "../log_create_main.cpp" "_CODE_FUNC" "int generate_event(const std::string&, const nlohmann::json_abi_v3_11_2::json&)" "_CODE_LINE" "34" "_PID" "2239596" emits-change writable
```

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I4f96370b9fb07664192e4fe09308cab170176213
diff --git a/elog_serialize.cpp b/elog_serialize.cpp
index 7d0a0aa..1fd5a1f 100644
--- a/elog_serialize.cpp
+++ b/elog_serialize.cpp
@@ -92,6 +92,7 @@
     e.timestamp(timestamp, true);
     e.message(message, true);
     e.additionalData(additionalData, true);
+    e.additionalData2(util::additional_data::parse(additionalData), true);
     e.sdbusplus::server::xyz::openbmc_project::logging::Entry::resolved(
         resolved, true);
     e.associations(associations, true);