How I can place connection metadata in order to trace my queries on RDS performance insights fot my postgresql db?
In many cases, the application_name setting is shown for connections. If your database driver does not allow to set it when creating the connection, you can execute
SET application_name = '...';

at any time.
If your panel shows only the query text, then you have to add the information to the query text:
/* Hi, Mom! */ SELECT 42;