Enable SSL connectivity to SQL storage

We are using following settings to store chat archive messages:

storage = “sql”
sql = {
driver = “PostgreSQL”; – May also be “MySQL” or “SQLite3” (case sensitive!)
database = “prosody”; – The database name to use. For SQLite3 this the database filename (relative to the data storage directory).
host = “localhost”; – The address of the database server (delete this line for Postgres)
port = 5432; – For databases connecting over TCP
username = “pdusr”; – The username to authenticate to the database
password = “****”; – The password to authenticate to the database
}

How to enable SSL connection for this?