Add example on how to pass a custom configuration for the Vert.x client

[DavideD]

We need to document with an example how it's possible to add a custom configuration for the Vert.x SQL client.
For example:

public class PgClientPoolConfiguration extends DefaultSqlClientPoolConfiguration {

    private static String HIBERNATE_VERTX_PGSQL_SSL = "hibernate.vertx.pgsql.ssl";
    private static String HIBERNATE_VERTX_PGSQL_SSL_MODE = "hibernate.vertx.pgsql.ssl.mode";

    private boolean ssl;
    private String sslMode;

    @Override
    public void configure(Map configuration) {
        super.configure(configuration);
        ssl = ConfigurationHelper.getBoolean(HIBERNATE_VERTX_PGSQL_SSL, configuration);
        sslMode = ConfigurationHelper.getString(HIBERNATE_VERTX_PGSQL_SSL_MODE, configuration);
    }

    @Override
    public SqlConnectOptions connectOptions(URI uri) {
        SqlConnectOptions sqlConnectOptions = super.connectOptions(uri);
        PgConnectOptions pgConnectOptions = new PgConnectOptions(sqlConnectOptions);

        if (ssl) {
            pgConnectOptions.setSsl(true);
            pgConnectOptions.setTrustAll(true);
            pgConnectOptions.setSslMode(SslMode.of(sslMode));
        }
        return pgConnectOptions;
    }
}

Related to this: #1108 (comment)