Add db connection debugging logging env

[zhouzhuojie]

Since the database connection error may contain credentials, we are adding this env to control whether we should log that error or not.

[ziru]

It seems to me that you want config.Config.DBConnectionDebug to gate the output of err field, instead of the whole log message.

Is the change below what you intended to make?

if err != nil {
  if config.Config.DBConnectionDebug {
    logrus.WithField("err", err).Fatal("failed to connect to db")
  } else {
    logrus.Fatal("failed to connect to db")
  }
}