The new event API in Broker enables users to install custom event
observers (loggers) in order to embed Broker logs into a wider context.

The new logging backend no longer offers trace logging. Since it is more
geared towards high-level description of events rather than leaving a
paper trail what lines of code ran.

The distinction between clones and masters at the log level component
has proven to be too fine-grained and makes it difficult to log events
outside of the master and clone actors, e.g., the store (base) actor or
the channels.