A libpq connection parameter providing a default application name
fallback_application_name is a libpq connection parameter providing an application name to use if
application_name is not set.
fallback_application_name was added in PostgreSQL 9.0.
fallback_application_name is an entirely discrectionary parameter which can be used as the client application sees fit.
In PostgreSQL 12 and later, if
cluster_name is set,
fallback_application_name will be set to that value when making a replication connection to the upstream node.