Removes all the logger::on_xxx functions
Removes the Logger template parameter to async_run
Adds a logger constructor that allows passing a std::function to customize logging behavior
Adds constructors to connection and basic_connection taking a logger
Deprecates config::logger_prefix
Deprecates the async_run overload taking a logger parameter
Deprecates the basic_connection::async_run overload not taking any config object
Deprecates the basic_connection::next_layer_type typedef
Makes the default log level logger::info
Makes the logging thread-safe
Cleans up deprecated functionality from examples
Adds docs on logging
Adds an example on how to integrate spdlog into Boost.Redis logging

close #213