Flogger implementation should not read the configuration twice

I think there is an issue in your implementation when the configuration is changed dynamically. Your implementation read the configuration twice, once in `at(Level)` and once later in `log()` so the logger can check the level of one configuration and log using another newly updated configuration.

To fix this issue, you can read the configuration once in `at()` and propagate the configuration as a parameter of the Context.