One thing to note about Logger.metadata is that it is set only for the current process. From the documentation
## Metadata
Metadata to be sent to the Logger can be read and written with the
Logger.metadata/0 and Logger.metadata/1 functions. For example, you can set
Logger.metadata([user_id: 13]) to add user_id metadata to the current process.
The user can configure the backend to chose which metadata it wants to print
and it will replace the $metadata value.
