✨ feature: integrate SSL mode for PG connections (#77)

Right now, the default connection for postgres is `disable`. Some
databases require `verify` or even `required`.
This PR introduces a new implementation that allows the user to override
the `disable` mode. The PR keeps a backwards compatible config entry, that
sets the default behavior to `disable` if it's missing.

postgres/postgres.go

@@ -57,9 +57,10 @@ func New(config ...Config) *Storage {
 		dsn += "@"
 	}
 	dsn += fmt.Sprintf("%s:%d", url.QueryEscape(cfg.Host), cfg.Port)
-	dsn += fmt.Sprintf("/%s?connect_timeout=%d&sslmode=disable",
+	dsn += fmt.Sprintf("/%s?connect_timeout=%d&sslmode=%s",
 		url.QueryEscape(cfg.Database),
 		int64(cfg.timeout.Seconds()),
+		cfg.SslMode,
 	)
 
 	// Create db